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Overview of IUGR FGR

Doctor at Shrikhande IVF & Surrogacy Centre
Jul. 5, 2021
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Overview of IUGR FGR

  1. • Chairperson Elect ICOG –Indian College of OB/GY • National Corresponding Editor-Journal of OB/GY of India JOGI • National Corresponding Secretary Association of Medical Women, India • Founder Patron & President –ISOPARB Vidarbha Chapter • Chairperson-IMS Education Committee 2021-23 • President-Association of Medical Women, Nagpur AMWN 2021-24 • Nagpur Ratan Award @ hands of Union Minister Shri Nitinji Gadkari • Received Bharat excellence Award for women’s health • Received Mehroo Dara Hansotia Best Committee Award for her work as Chairperson HIV/AIDS Committee, FOGSI 2007-2009 • Received appreciation letter from Maharashtra Government for her work in the field of SAVE THE GIRL CHILD • Senior Vice President FOGSI 2012 • President Menopause Society, Nagpur 2016-18 • President Nagpur OB/GY Society 2005-06 • Delivered 11 orations and 450 guest lectures • Publications-Thirty National & Eleven International • Sensitized 2 lakh boys and girls on adolescent health issues Dr. Laxmi Shrikhande MBBS; MD(OB/GY); FICOG; FICMU; FICMCH Medical Director- Shrikhande Fertility Clinic Nagpur, Maharashtra
  2. OVERVIEW OF IUGR
  3. What do we mean by FGR ?  Fetal growth restriction (FGR, also called IUGR) is the term used to describe a fetus that has not reached its growth potential because of environmental factors.  The origin of the problem may be fetal, placental, or maternal, with significant overlap among these entities.
  4. Definition The most common obstetric definition of FGR is based on sonography: an estimated fetal weight below the 10th percentile for gestational age; however, other definitions using a variety of criteria have been proposed. Society for Maternal-Fetal Medicine (SMFM). Electronic address: pubs@smfm.org, Martins JG, Biggio JR, Abuhamad A. Society for Maternal-Fetal Medicine Consult Series #52: Diagnosis and management of fetal growth restriction: (Replaces Clinical Guideline Number 3, April 2012). Am J Obstet Gynecol 2020; 223:B2.
  5. FGR: Screening and diagnosis-What's new ?  Fetal abdominal circumference <10th percentile for diagnosis of growth restriction (March 2021)  Updated guidance from the Society for Maternal-Fetal Medicine and the American College of Obstetricians and Gynecologists now considers abdominal circumference <10th percentile for gestational age another acceptable threshold for suspecting FGR .  Note that the lower the percentile, the more likely the diagnosis of FGR rather than a constitutionally small fetus. American College of Obstetricians and Gynecologists Committee on Practice Bulletins—Obstetrics, Society for Maternal-Fetal Medicine Publications Committee. Fetal Growth Restriction: ACOG Practice Bulletin, Number 227. Obstet Gynecol 2021; 137:e16.
  6. Limitations  The use of a percentile to define FGR is problematic because it does not distinguish among fetuses who are constitutionally small versus SGA.  As many as 70 percent of fetuses estimated to weigh below the 10th percentile for gestational age are small simply due to constitutional factors (eg, maternal ethnicity, parity, or body mass index) and are not at high risk of perinatal mortality and morbidity .  There is a real possibility of misclassifying these normally nourished, healthy, but constitutionally small, fetuses as growth restricted. Manning FA. Intrauterine growth retardation. In: Fetal Medicine: Principal an d Practice, Appleton & Lange, Norwalk, CT 1995. p.317.
  7. Limitations  An additional problem is that use of percentiles requires an appropriate reference, but there is little consensus on which reference should be used.  Ultrasound-based standards avoid this bias but are limited by the inaccuracy and imprecision of ultrasound-EFW. Zhang J, Merialdi M, Platt LD, Kramer MS. Defining normal and abnormal fetal growth: promises and challenges. Am J Obstet Gynecol 2010; 202:522. Ananth CV, Brandt JS, Vintzileos AM. Standard vs population reference curves in obstetrics: which one should we use? Am J Obstet Gynecol 2019; 220:293.
  8. Classification Regardless of the FGR definition used, FGR may be classified as early or late and as symmetric or asymmetric:  Early FGR refers to diagnosis before 32 weeks of gestation, in the absence of congenital anomalies.  Late FGR refers to diagnosis at ≥32 weeks of gestation, in the absence of congenital anomalies.
  9. Classification  Symmetric FGR comprises 20 to 30 percent of FGR and refers to a growth pattern in which all fetal organs are decreased proportionally due to global impairment of cellular hyperplasia early in gestation.  Symmetric FGR is thought to result from a pathologic process manifesting early in gestation.  Asymmetric FGR comprises the remaining 70 to 80 percent of the FGR population and is characterized by a relatively greater decrease in abdominal size (eg, liver volume and subcutaneous fat tissue) than in head circumference.  Asymmetric fetal growth is thought to result from the capacity of the fetus to adapt to a pathologic environment late in gestation by redistributing blood flow in favor of vital organs (eg, brain, heart, placenta) at the expense of nonvital fetal organs (eg, abdominal viscera, lungs, skin, kidneys) .  Undoubtedly, some overlap exists between these two entities. Uerpairojkit B, Chan L, Reece AE, et al. Cerebellar Doppler velocimetry in the appropriate- and small-for-gestational-age fetus. Obstet Gynecol 1996; 87:989. Bahado-Singh RO, Kovanci E, Jeffres A, et al. The Doppler cerebroplacental ratio and perinatal outcome in intrauterine growth restriction. Am J Obstet Gynecol 1999; 180:750.
  10. Screening  Rationale — Ideally, prenatal detection of FGR will provide an opportunity to employ interventions to reduce the morbidity and mortality associated with this problem.  Adverse outcomes include fetal demise, preterm birth, perinatal asphyxia, poor thermoregulation, hypoglycemia, polycythemia/hyperviscosity, impaired immune function, neonatal death, neurodevelopmental delay, and some adult-onset disorders.  the ability of screening and appropriate intervention to reduce the frequency of any of these outcomes has not been proven.  Harms of screening include overdiagnosis of FGR, leading to parental anxiety and unnecessary, costly, and/or potentially harmful interventions (eg, antenatal fetal testing, induction of labor, iatrogenic preterm delivery).
  11. How to screen ?
  12. Symphysis-fundal height measurement with selective ultrasonography —  The first suspicion of FGR often arises when this length is noted to be discordant with the expected size for dates.  Discordancy has been defined in various ways; the most common criterion is a fundal height in centimeters that is at least 3 centimeters less than the gestational age in weeks (eg, fundal height 32 cm at 36 weeks of gestation)  Alternatively, a fundal height measurement below the 3rd or 10th percentile for gestational age can be used: The INTERGROWTH- 21st Project International published printable symphysis-fundal height measurement standards for the 3rd, 10th, 50th, 90th, and 97th percentiles using eight urban populations of healthy, well-nourished women. Papageorghiou AT, Ohuma EO, Gravett MG, et al. International standards for symphysis-fundal height based on serial measurements from the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project: prospective cohort study in eight countries. BMJ 2016; 355:i5662.
  13. Symphysis-fundal height measurement with selective ultrasonography —  The performance of fundal height measurements for screening for FGR is controversial.  A systematic review concluded evidence was inadequate (one randomized trial) to evaluate the effectiveness of this technique versus abdominal palpation for detecting abnormal fetal growth .  Robert Peter J, Ho JJ, Valliapan J, Sivasangari S. Symphysial fundal height (SFH) measurement in pregnancy for detecting abnormal fetal growth. Cochrane Database Syst Rev 2015; :CD008136.  Observational studies using symphysis pubis-fundal height measurements have reported a wide range of sensitivities: 13 to 86 percent of small fetuses were detected . Factors that may affect sensitivity include maternal body mass index, bladder volume, parity, and ethnic group. Goetzinger KR, Tuuli MG, Odibo AO, et al. Screening for fetal growth disorders by clinical exam in the era of obesity. J Perinatol 2013; 33:352.
  14. Symphysis-fundal height measurement with selective ultrasonography — • This technique appears to perform best when all of the measurements are obtained by the same clinician using the unmarked side of the tape (to reduce bias ) and plotted to reflect fetal growth for the individual patient ("customized"), rather than against a standardized norm . Roex A, Nikpoor P, van Eerd E, et al. Serial plotting on customised fundal height charts results in doubling of the antenatal detection of small for gestational age fetuses in nulliparous women. Aust N Z J Obstet Gynaecol 2012; 52:78.
  15. Universal ultrasonography  Routine universal performance of ultrasound examination is an alternative method of screening for FGR.  There is no consensus on the timing or number of screening examinations. Deter RL, Lee W, Yeo L, et al. Individualized growth assessment: conceptual framework and practical implementation for the evaluation of fetal growth and neonatal growth outcome. Am J Obstet Gynecol 2018; 218:S656.
  16. Universal ultrasonography  In general, if two screening examinations are performed after the 18- to 22-week fetal anatomic survey, they are obtained at approximately 32 and 36 weeks of gestation .  If one examination is obtained, it is obtained between 32 and 36 weeks of gestation, and the predictive performance is higher nearer to 36 weeks . Bricker L, Medley N, Pratt JJ. Routine ultrasound in late pregnancy (after 24 weeks' gestation). Cochrane Database Syst Rev 2015; :CD001451. Ciobanu A, Khan N, Syngelaki A, et al. Routine ultrasound at 32 vs 36 weeks' gestation: prediction of small-for-gestational- age neonates. Ultrasound Obstet Gynecol 2019; 53:761.
  17. Approach to screening for fetal growth restriction in singleton pregnancies in the third trimester
  18. Evidence — Universal ultrasonography  In a 2019 meta-analysis of 21 cohort studies of screening ultrasound at ≥32 weeks of gestation in low-risk or non selected singleton pregnancies, Modeled sensitivities of AC and EFW <10th percentile at a 10 percent false- positive rate were 78 and 54 percent, respectively.  In a meta-analysis of 13 controlled trials including nearly 35,000 women, perinatal mortality was similar for patients undergoing routine versus no/concealed/selective ultrasonography (risk ratio 1.01, 95% CI 0.67-1.54); none of the trials reported on neurodevelopmental outcomes at age 2 .  A subsequent prospective study reported sensitivity for detection of small for gestational age infants was higher with universal than with selective ultrasound screening, but this did not lead to a significant reduction in composite severe adverse perinatal outcome . Caradeux J, Martinez-Portilla RJ, Peguero A, et al. Diagnostic performance of third-trimester ultrasound for the prediction of late-onset fetal growth restriction: a systematic review and meta-analysis. Am J Obstet Gynecol 2019; 220:449. Sovio U, White IR, Dacey A, et al. Screening for fetal growth restriction with universal third trimester ultrasonography in nulliparous women in the Pregnancy Outcome Prediction (POP) study: a prospective cohort study. Lancet 2015; 386:2089.
  19. Special populations- sub optimally dated pregnancies  When the gestational age is not known with reasonable certainty, a single ultrasound examination may not be able to distinguish a small for gestational age fetus from an appropriately grown fetus that is less far along in gestation than expected from menstrual dates.  Serial sonographic examinations at two-week intervals can be useful when pregnancy dating is suboptimal. Deter RL, Lee W, Kingdom JCP, Romero R. Fetal growth pathology score: a novel ultrasound parameter for individualized assessment of third trimester growth abnormalities. J Matern Fetal Neonatal Med 2018; 31:866.
  20. Special populations- Multiple gestation  Growth in multiple gestations diverges from that in singletons in the late second or early third trimester.  Smallness of one or both fetuses of a multiple gestation can be related to any of the disorders that cause FGR in singleton pregnancies, as well as disorders unique to multiple gestations, such as unequal placental sharing or twin-twin transfusion.
  21. Fetal growth restriction: Evaluation and management
  22. Initial approach- Confirm the diagnosis Characteristics that support a diagnosis of a constitutionally small fetus include:  Modest smallness (ie, EFW between the 5th and 10th percentiles)  Normal growth velocity across gestation  Normal physiology (ie, normal amniotic fluid volume and umbilical artery Doppler)  Abdominal circumference growth velocity above the 10th percentile  Appropriate size in relation to maternal characteristics (height, weight, race/ethnicity) Society for Maternal-Fetal Medicine (SMFM). Electronic address: pubs@smfm.org, Martins JG, Biggio JR, Abuhamad A. Society for Maternal-Fetal Medicine Consult Series #52: Diagnosis and management of fetal growth restriction: (Replaces Clinical Guideline Number 3, April 2012). Am J Obstet Gynecol 2020; 223:B2. Dubinsky TJ, Sonneborn R. Trouble With the Curve: Pearls and Pitfalls in the Evaluation of Fetal Growth. J Ultrasound Med 2020; 39:1839.
  23. Initial approach- Confirm the diagnosis  Maternal characteristics have a major influence on fetal growth potential.  For example, when race/ethnicity was taken into account, the 5th percentiles for White, Hispanic, Black, and Asian women were 2790, 2633, 2622, and 2621 grams, respectively, in a prospective study of over 2300 healthy women with low-risk, singleton pregnancies from 12 medical centers in the United States . Buck Louis GM, Grewal J, Albert PS, et al. Racial/ethnic standards for fetal growth: the NICHD Fetal Growth Studies. Am J Obstet Gynecol 2015; 213:449.e1.
  24. Initial approach- Confirm the diagnosis  Using a lower threshold to define FGR may help distinguish the small fetus at increased risk of adverse outcome from the small fetus at low risk.  Use of a lower threshold for defining pathologic FGR is supported by several studies. Unterscheider J, Daly S, Geary MP, et al. Optimizing the definition of intrauterine growth restriction: the multicenter prospective PORTO Study. Am J Obstet Gynecol 2013; 208:290.e1. Mlynarczyk M, Chauhan SP, Baydoun HA, et al. The clinical significance of an estimated fetal weight below the 10th percentile: a comparison of outcomes of <5th vs 5th-9th percentile. Am J Obstet Gynecol 2017; 217:198.e1.
  25. Initial approach- Confirm the diagnosis  In a retrospective study, composite fetal morbidity at <5th percentile versus 5th to 10th percentile was 39 and 13 percent, respectively (odds ratio 2.41, 95% CI 1.5-3.8) .  Although using <5th percentile as a threshold for FGR captures the group of fetuses at highest risk for adverse outcome, those at the 5th to 10th percentile still need to be monitored closely since not all are constitutionally small. Mlynarczyk M, Chauhan SP, Baydoun HA, et al. The clinical significance of an estimated fetal weight below the 10th percentile: a comparison of outcomes of <5th vs 5th-9th percentile. Am J Obstet Gynecol 2017; 217:198.e1.
  26. Determine the cause —  The genetically predetermined growth potential of the fetus can be impaired as a result of maternal, placental, or fetal processes .  To determine the cause of FGR, a complete history and physical examination is performed to assess for maternal disorders that have been associated with restricted fetal growth.  In addition, obstetric imaging and laboratory evaluations are performed to look for fetal and placental etiologies.  However, the reason(s) for growth impairment cannot always be determined ante natally. Mateus J, Newman RB, Zhang C, et al. Fetal growth patterns in pregnancy-associated hypertensive disorders: NICHD Fetal Growth Studies. Am J Obstet Gynecol 2019; 221:635.e1.
  27. Fetal survey –  A detailed fetal anatomic survey should be performed in all cases since approximately 10 percent of FGR is accompanied by congenital anomalies and 20 to 60 percent of malformed infants are SGA .  Anomalies associated with FGR include omphalocele, gastroschisis, diaphragmatic hernia, skeletal dysplasia, and some congenital heart defects.  A fetal echocardiogram is indicated if results of an expert (level II) ultrasound examination suggest any uncertainty that the heart is normal.
  28. Fetal genetic studies – Fetal genetic studies are indicated in any of the following settings because of the increased risk of an abnormality:  FGR that is all of the following: Early (<24 weeks), severe (<5th percentile), and symmetrical.  FGR with major fetal structural abnormalities.  FGR with soft ultrasound markers associated with an increased risk of aneuploidy, such as thickened nuchal fold/choroid plexus cyst and abnormal hand positioning.  Placental findings suggestive of a partial molar pregnancy: Enlarged, cystic spaces ("Swiss cheese pattern") and/or increased echogenicity of chorionic villi.
  29. Fetal genetic studies –  The American College of Obstetricians and Gynecologists suggests genetic counseling and offering diagnostic testing for patients with diagnosis of FGR before 32 weeks or FGR in combination with polyhydramnios or fetal malformation .  Ultrasound examination has high sensitivity for identifying trisomy 18, as high as 100 percent, when performed by an experienced ultrasonographer at 19 to 20 weeks of gestation in a fetus with multiple structural anomalies characteristic of the syndrome. American College of Obstetricians and Gynecologists Committee on Practice Bulletins— Obstetrics, Society for Maternal-Fetal Medicine Publications Committee. Fetal Growth Restriction: ACOG Practice Bulletin, Number 227. Obstet Gynecol 2021; 137:e16.
  30. Fetal genetic studies –  Although the finding of symmetrical FGR prior to 24 weeks of gestation is associated with a high risk of aneuploidy, this is no longer the case later in gestation .  After 24 weeks, we do not screen for fetal genetic abnormalities if anatomy is normal and FGR is asymmetric since the yield would be low, the etiology is most likely a maternal or placental disorder, and pregnancy termination is generally not an option.  In a systematic review of 14 observational cohort studies including 874 apparently isolated FGR cases, the mean rate of chromosome anomalies was 6.4 percent (range 0 to 26 percent), and no abnormal karyotypes were found in the two studies of apparently isolated FGR diagnosed in the third trimester (32 pregnancies). Meler E, Sisterna S, Borrell A. Genetic syndromes associated with isolated fetal growth restriction. Prenat Diagn 2020; 40:432. Sagi-Dain L, Peleg A, Sagi S. Risk for chromosomal aberrations in apparently isolated intrauterine growth restriction: A systematic review. Prenat Diagn 2017; 37:1061.
  31. Work-up for infection –  Infections associated with FGR include cytomegalovirus, toxoplasmosis, rubella, and varicella. Amniotic fluid DNA testing can also be performed for specific infections when indicated by the clinical setting.  Malaria in pregnancy can also cause FGR and should be considered in endemic areas  Maternal COVID-19 does not appear to be associated with an increased prevalence of FGR . However, data on perinatal outcomes when the infection is acquired in early pregnancy are limited, and any condition that results in prolonged maternal hypoxia places the fetus at risk for growth restriction. Dashraath P, Wong JLJ, Lim MXK, et al. Coronavirus disease 2019 (COVID-19) pandemic and pregnancy. Am J Obstet Gynecol 2020; 222:521. Di Mascio D, Khalil A, Saccone G, et al. Outcome of coronavirus spectrum infections (SARS, MERS, COVID- 19) during pregnancy: a systematic review and meta-analysis. Am J Obstet Gynecol MFM 2020; 2:100107.
  32. Work-up for antiphospholipid syndrome –  Although early-onset placental insufficiency is one of the clinical criteria for the diagnosis of APS by expert consensus , a link between antiphospholipid antibodies alone and FGR has not been established, and there is insufficient evidence to support screening all women with FGR for these antibodies.  Indications for screening include a past history of fetal loss and prior unexplained arterial or venous thromboembolism. Committee on Practice Bulletins—Obstetrics, American College of Obstetricians and Gynecologists. Practice Bulletin No. 132: Antiphospholipid syndrome. Obstet Gynecol 2012; 120:1514. Reaffirmed 2019.
  33. Pregnancy management  Pregnancy management of FGR in structurally and chromosomally normal fetuses-  Most of these cases are caused by uteroplacental insufficiency.  Management of FGR associated with congenital or chromosomal anomalies depends on the specific abnormality and is beyond the scope of this presentation.
  34. Pregnancy management The optimal management of the pregnancy with suspected growth restriction related to uteroplacental insufficiency consists of serial ultrasound evaluation of:  Fetal growth velocity  Fetal behavior (biophysical profile [BPP])  Impedance to blood flow in fetal arterial and venous vessels (Doppler velocimetry)
  35. Pregnancy management The purpose is to identify those fetuses who are at highest risk of perinatal demise and who may benefit from delivery. Hugh O, Williams M, Turner S, Gardosi J. Reduction of stillbirths in England from 2008 to 2017 according to uptake of the Growth Assessment Protocol: 10-year population-based cohort study. Ultrasound Obstet Gynecol 2021; 57:401.
  36. Ambulatory monitoring —  Women with pregnancies complicated by FGR may maintain normal activities and are usually monitored as outpatients.  There are no data on which to base indications for hospitalization.  consider hospitalization for selected women who need daily or more frequent maternal or fetal assessment (eg, daily BPP score because of reversed diastolic flow).  Hospitalization provides convenient access for daily fetal testing and allows prompt evaluation and intervention in the event of decreased fetal activity or other complications, but there is no evidence that hospitalization or bed rest improves fetal growth or outcome . Lausman A, McCarthy FP, Walker M, Kingdom J. Screening, diagnosis, and management of intrauterine growth restriction. J Obstet Gynaecol Can 2012; 34:17.
  37. Ambulatory monitoring —  Although decisions about selecting women for ambulatory versus in- hospital care should be made on a case-by-case basis, we generally admit women with absent/reversed flow of the umbilical artery and estimated fetal weight (EFW) >350 grams.  This cutoff is based on our experience of good short- and long-term outcomes in such cases.  However, the cutoff weight for monitoring varies among institutions. Gülmezoglu AM, Hofmeyr GJ. Bed rest in hospital for suspected impaired fetal growth. Cochrane Database Syst Rev 2000; :CD000034.
  38. Antenatal corticosteroids —  Ideally, a course of antenatal betamethasone is given to pregnancies <34+0 weeks of gestation in the week before preterm delivery is anticipated.  Administration at 34+0 to 36+6 weeks does not appear to decrease the need for respiratory support and increases the rate of neonatal hypoglycemia but is recommended by some guidelines .  Timing is estimated based on multiple factors, including the severity of FGR, Doppler findings, comorbid conditions, and rate of deterioration in fetal status. Bitar G, Merrill SJ, Sciscione AC, Hoffman MK. Antenatal corticosteroids in the late preterm period for growth-restricted pregnancies. Am J Obstet Gynecol MFM 2020; 2:100153.
  39. Maternal interventions —  There is no convincing evidence that any intervention in healthy women improves the growth of growth-restricted fetuses.  Numerous approaches have been tried in small randomized trials, including maternal nutritional supplementation, oxygen therapy, and interventions to improve blood flow to the placenta, such as plasma volume expansion, low-dose aspirin, bed rest, and anticoagulation . Gülmezoglu AM, Hofmeyr GJ. Maternal nutrient supplementation for suspected impaired fetal growth. Cochrane Database Syst Rev 2000; :CD000148. Gülmezoglu AM, Hofmeyr GJ. Maternal oxygen administration for suspected impaired fetal growth. Cochrane Database Syst Rev 2000; :CD000137.
  40. Maternal interventions —Sildanafil  appeared promising and was under investigation.  However, a multicenter Dutch trial of sildenafil for treatment of poor prognosis early-onset FGR was halted early because of a higher than expected rate of pulmonary hypertension in the intervention group with no benefit in the primary outcome (perinatal mortality or major neonatal morbidity) at the time the trial was stopped.  A concurrent trial in Australia and New Zealand reported sildenafil had no effect on fetal growth velocity after diagnosis of growth restriction before 30 weeks but no adverse effects on newborns. Pels A, Derks J, Elvan-Taspinar A, et al. Maternal Sildenafil vs Placebo in Pregnant Women With Severe Early-Onset Fetal Growth Restriction: A Randomized Clinical Trial. JAMA Netw Open 2020; 3:e205323. Groom KM, McCowan LM, Mackay LK, et al. STRIDER NZAus: a multicentre randomised controlled trial of sildenafil therapy in early-onset fetal growth restriction. BJOG 2019; 126:997.
  41. Maternal interventions —  In hypertensive pregnant women, antihypertensive therapy does not improve fetal growth .  In smokers, an intensive smoking cessation program may be of value and has other pregnancy and health benefits . Abalos E, Duley L, Steyn DW. Antihypertensive drug therapy for mild to moderate hypertension during pregnancy. Cochrane Database Syst Rev 2014; :CD002252. Figueras F, Meler E, Eixarch E, et al. Association of smoking during pregnancy and fetal growth restriction: subgroups of higher susceptibility. Eur J Obstet Gynecol Reprod Biol 2008; 138:171. Aagaard-Tillery KM, Porter TF, Lane RH, et al. In utero tobacco exposure is associated with modified effects of maternal factors on fetal growth. Am J Obstet Gynecol 2008; 198:66.e1.
  42. Timing delivery —GRIT Trial  There is little consensus about the optimum time to deliver the growth-restricted fetus.  The following key trials attempted to answer the question of when to intervene in these pregnancies, without a clear conclusion:  The Growth Restriction Intervention Trial (GRIT) randomly assigned pregnant women between 24 and 36 weeks with FGR to immediate (n = 296) or delayed (n = 291) delivery if their obstetrician was uncertain about when to intervene . Forty percent of these pregnancies had absent or reversed end-diastolic umbilical artery flow. In the delayed delivery group, delivery occurred when the obstetrician was no longer uncertain about intervening, which took a median 4.9 days.  The immediate delivery group had fewer stillbirths (2 versus 9 with delayed delivery) but more neonatal and infant deaths (27 versus 18), especially when randomization occurred before 31 weeks. Follow-up data up to age 13 years showed no differences between groups in cognition, language, motor, or parent-assessed behavior scores on standardized tests; follow-up was achieved in approximately 70 percent of survivors . Cognition scores were close to the standardized normal range. Walker DM, Marlow N, Upstone L, et al. The Growth Restriction Intervention Trial: long-term outcomes in a randomized trial of timing of delivery in fetal growth restriction. Am J Obstet Gynecol 2011; 204:34.e1.
  43. Timing delivery —DIGITAT Trial  The Disproportionate Intrauterine Growth Intervention Trial At Term trial (DIGITAT) randomly assigned 650 pregnant women over 36.0 weeks of gestation with suspected FGR to induction of labor or expectant monitoring .  The primary outcome was a composite measure of adverse neonatal outcome (death before hospital discharge, five-minute Apgar score <7, umbilical artery pH <7.05, or admission to the intensive care unit) . Neonatal morbidity was analyzed separately using Morbidity Assessment Index for Newborns (MAIN) score .  The authors concluded that both approaches were reasonable, and the choice should depend on patient preference. However, in a sub analysis of the data, they also reported that neonatal admissions were lower when growth restricted fetuses were delivered after 38 weeks of gestation , which suggests a benefit of deferring delivery until 38 weeks of gestation, as long as the fetus is closely monitored and in the absence of other indications for an early delivery. Boers KE, van Wyk L, van der Post JA, et al. Neonatal morbidity after induction vs expectant monitoring in intrauterine growth restriction at term: a subanalysis of the DIGITAT RCT. Am J Obstet Gynecol 2012; 206:344.e1.
  44. Timing delivery —TRUFFLE Study  TRUFFLE assessed whether changes in the fetal ductus venosus Doppler waveform could be used to guide timing of delivery of growth-restricted fetuses with a high umbilical artery Doppler pulsatility index (>95th percentile) instead of the conventional approach using cardiotocography short-term variation (STV) .  The primary outcome measure was survival without neurodevelopmental impairment at two years of age. Pregnancies were randomly assigned to one of three monitoring approaches: cardiotocography with delivery for reduced STV, ductus venosus monitoring with delivery for early ductus venosus changes (pulsatility index >95th percentile), or ductus venosus monitoring with delivery for late ductus venosus changes (a-wave indicating absent or reversed flow).  Their observations clearly demonstrate the need for additional study of the most appropriate methods to determine delivery timing in the very preterm (<32 weeks of gestation) FGR fetus. Visser GHA, Bilardo CM, Derks JB, et al. Fetal monitoring indications for delivery and 2-year outcome in 310 infants with fetal growth restriction delivered before 32 weeks' gestation in the TRUFFLE study. Ultrasound Obstet Gynecol 2017; 50:347.
  45. Route of delivery —  An unfavorable cervix is not a reason to avoid induction.  In a secondary analysis of data from the DIGITAT and HYPITAT trials (pregnancies complicated by FGR and hypertension), induction of labor at term in women with median Bishop scores of 3 (range 1 to 6) was not associated with a higher rate of cesarean delivery than expectant management, and approximately 85 percent of women in both groups achieved a vaginal delivery . Prostaglandins or a balloon catheter was used for cervical ripening.  In a meta-analysis of observational studies of labor induction with misoprostol, dinoprostone, or mechanical methods in FGR, mechanical methods appeared to be associated with a lower occurrence of adverse intrapartum outcomes, but a direct comparison among methods could not be performed.  However, when the indication for delivery is persistent reversed flow of the umbilical artery, we give patients the option of a scheduled cesarean birth, especially when the cervix is unfavorable, because many of these fetuses will not tolerate labor and we wish to avoid adding an acute insult on a chronic hypoxic fetus. Bernardes TP, Broekhuijsen K, Koopmans CM, et al. Caesarean section rates and adverse neonatal outcomes after induction of labour versus expectant management in women with an unripe cervix: a secondary analysis of the HYPITAT and DIGITAT trials. BJOG 2016; 123:1501. Familiari A, Khalil A, Rizzo G, et al. Adverse intrapartum outcome in pregnancies complicated by small for gestational age and late fetal growth restriction undergoing induction of labor with Dinoprostone, Misoprostol or mechanical methods: A systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol 2020; 252:455.
  46. Intrapartum management  It is important to optimize the timing of delivery, perform continuous intrapartum fetal monitoring to detect non reassuring fetal heart rate patterns suggestive of progressive hypoxia during labor, and provide skilled neonatal care in the delivery room . Umbilical cord blood analysis should be considered as a component of establishing baseline neonatal status  If antenatal testing (non stress test or biophysical profile) is normal, a trial of labor with continuous intrapartum monitoring is reasonable .  However, the frequency of cesarean delivery for non reassuring fetal heart rate tracing is increased, given the increased prevalence of chronic hypoxia and oligohydramnios among these fetuses. Werner EF, Savitz DA, Janevic TM, et al. Mode of delivery and neonatal outcomes in preterm, small-for-gestational-age newborns. Obstet Gynecol 2012; 120:560. Chauhan SP, Weiner SJ, Saade GR, et al. Intrapartum Fetal Heart Rate Tracing Among Small-for-Gestational Age Compared With Appropriate-for-Gestational-Age Neonates. Obstet Gynecol 2018; 132:1019.
  47. Intrapartum management • For fetuses less than 32 weeks of gestation, magnesium sulfate is given before delivery for neuroprotection. • When use of magnesium sulfate was studied specifically in pregnancies with growth-restricted fetuses, a decrease in significant neurodevelopmental impairment and death was observed. Stockley EL, Ting JY, Kingdom JC, et al. Intrapartum magnesium sulfate is associated with neuroprotection in growth-restricted fetuses. Am J Obstet Gynecol 2018; 219:606.e1.
  48. Prognosis  Fetal, newborn, and childhood outcomes — Fetal demise, neonatal death, neonatal morbidity, and abnormal neurodevelopmental outcome are more common in growth-restricted fetuses than in those with normal growth .  The prognosis worsens with early-onset FGR, increasing severity of growth restriction , and absent or reversed end-diastolic flow on umbilical artery Doppler .  In a systematic review of studies of FGR diagnosed before 32 weeks of gestation (n = 2895 pregnancies delivered after 2000), the frequencies of fetal and neonatal death were 12 and 8 percent, respectively . The most common neonatal morbidities were respiratory distress syndrome (34 percent), retinopathy of prematurity (13 percent), and sepsis (30 percent). Chauhan SP, Rice MM, Grobman WA, et al. Neonatal Morbidity of Small- and Large-for-Gestational- Age Neonates Born at Term in Uncomplicated Pregnancies. Obstet Gynecol 2017; 130:511.
  49. Prognosis-Fetal & Newborn  Fetal, newborn, and childhood outcomes — Among children who underwent neurodevelopmental assessment, 12 percent were diagnosed with cognitive impairment and/or cerebral palsy. The quality of evidence was generally rated as very low to moderate, except for three large, well-designed, randomized trials.  When all pregnancies with FGR are considered, regardless of gestational age at diagnosis, the risk of fetal death is approximately 1.5 percent at <10th percentile and 2.5 percent at <5th percentile for gestational age Delorme P, Kayem G, Lorthe E, et al. Neurodevelopment at 2 years and umbilical artery Doppler in cases of very preterm birth after prenatal hypertensive disorder or suspected fetal growth restriction: EPIPAGE-2 prospective population-based cohort study. Ultrasound Obstet Gynecol 2020; 56:557. Pels A, Beune IM, van Wassenaer-Leemhuis AG, et al. Early-onset fetal growth restriction: A systematic review on mortality and morbidity. Acta Obstet Gynecol Scand 2020; 99:153.
  50. Prognosis-Childhood  Longer term outcomes — An association has been observed between poor fetal growth, early accelerated postnatal growth, and later development of obesity, metabolic dysfunction, insulin sensitivity, type 2 diabetes, and cardiovascular and renal diseases (eg, coronary heart disease, hypertension, chronic kidney disease).  This association has been attributed to partial resetting of fetal metabolic homeostasis and endocrine systems in response to in utero nutritional deprivation. The combination of prematurity and severe FGR increases the risk of long-term neurodevelopmental abnormalities and decreased cognitive performance. Youssef L, Miranda J, Paules C, et al. Fetal cardiac remodeling and dysfunction is associated with both preeclampsia and fetal growth restriction. Am J Obstet Gynecol 2020; 222:79.e1. Timpka S, Macdonald-Wallis C, Hughes AD, et al. Hypertensive Disorders of Pregnancy and Offspring Cardiac Structure and Function in Adolescence. J Am Heart Assoc 2016; 5.
  51. Prognosis-Maternal  Maternal — The birth of a newborn with idiopathic growth restriction may be predictive of an increased long-term maternal risk for cardiovascular disease (coronary artery disease, myocardial infarction, coronary revascularization, peripheral arterial disease, transient ischemic attack, stroke).  A systematic review of 10 cohort studies found a consistent trend of an increased risk of cardiovascular disease-related morbidity and mortality in patients with a history of birth of an SGA infant compared to those with no such history (range of odds ratios 1.09 to 3.50) .  Pooling was not performed because of variations in the exposure definition among studies. Grandi SM, Filion KB, Yoon S, et al. Cardiovascular Disease-Related Morbidity and Mortality in Women With a History of Pregnancy Complications. Circulation 2019; 139:1069.
  52. Recurrence risk  There is a tendency to repeat small for gestational age (SGA) deliveries in successive pregnancies.  A prospective national cohort study from the Netherlands reported that the risk of a non anomalous SGA birth (<5th percentile) in the second pregnancy of women whose first delivery was "SGA" versus "not SGA" was 23 and 3 percent, respectively .  The association between the birth of an SGA infant in a first pregnancy and stillbirth in a subsequent pregnancy was illustrated by analysis of data from the Swedish Birth Register ; subsequent studies from the United States and Australia reported similar findings .  The highest risk of stillbirth was in women who delivered a preterm SGA infant.  Another series suggested a sibling delivered after the birth of an SGA infant (even if mildly SGA) was at increased risk of sudden infant death syndrome. Gordon A, Raynes-Greenow C, McGeechan K, et al. Stillbirth risk in a second pregnancy. Obstet Gynecol 2012; 119:509. Smith GC, Wood AM, Pell JP, Dobbie R. Sudden infant death syndrome and complications in other pregnancies. Lancet 2005; 366:2107.
  53. Prevention in subsequent pregnancies —  Address any potentially treatable causes of FGR (eg, cessation of smoking and alcohol intake, chemoprophylaxis and mosquito avoidance in areas where malaria is prevalent, balanced energy/protein supplementation in women with significant nutritional deficiencies.  Avoiding a short or long interpregnancy interval may also be beneficial.  Low-dose aspirin may be effective when FGR is secondary to preeclampsia since aspirin appears to reduce the risk of developing preeclampsia in women at moderate to high risk of developing the disorder.  In a meta-analysis of 45 randomized trials of low dose aspirin for prevention of preeclampsia and FGR in women at high risk, aspirin prophylaxis markedly reduced the incidence of FGR (relative risk [RR] 0.56, 95% CI 0.44-0.70) compared with placebo/no treatment .  Low-dose aspirin is not recommended in the absence of risk factors for PIH Roberge S, Nicolaides K, Demers S, et al. The role of aspirin dose on the prevention of preeclampsia and fetal growth restriction: systematic review and meta-analysis. Am J Obstet Gynecol 2017; 216:110. ACOG Committee Opinion No. 743: Low-Dose Aspirin Use During Pregnancy. Obstet Gynecol 2018; 132:e44.
  54. Prevention in subsequent pregnancies —  Anticoagulation with unfractionated heparin or low molecular weight heparin does not reduce the risk of recurrent placenta-mediated late pregnancy complications, such as growth restriction.  In a 2016 meta-analysis using individual patient data from randomized trials of low molecular weight heparin (LMWH) therapy versus no LMWH for women with any prior placenta-mediated pregnancy complications, the intervention did not significantly reduce the incidence of the primary composite outcome (early-onset or severe preeclampsia, SGA <5th percentile, abruption, pregnancy loss ≥20 weeks of gestation): 62/444 (14 percent) versus 95/443 (22 percent), RR 0.64, 95% CI 0.36-1.11 .  These data support avoidance of anticoagulation in women with previous placenta- mediated disease, given the lack of clear benefit and potential risks of anticoagulation, cost, and inconvenience. The combination of low dose aspirin and LMWH does not appear to be more effective than aspirin alone .  Dietary changes and supplements, antihypertensive therapy of hypertensive women, beta-mimetics, and bedrest do not prevent FGR . Rodger MA, Gris JC, de Vries JIP, et al. Low-molecular-weight heparin and recurrent placenta-mediated pregnancy complications: a meta- analysis of individual patient data from randomised controlled trials. Lancet 2016; 388:2629. Groom KM, McCowan LM, Mackay LK, et al. Enoxaparin for the prevention of preeclampsia and intrauterine growth restriction in women with a history: a randomized trial. Am J Obstet Gynecol 2017; 216:296.e1.
  55. Management of subsequent pregnancies —  Accurate dating by early ultrasonography is important to establish gestational age and intermittent ultrasound examinations are used to monitor fetal growth.  Otherwise, prenatal management is routine.  If fetal growth is normal, FGR in a previous pregnancy is not an indication for antepartum fetal surveillance with non stress tests, biophysical profiles, or umbilical artery Doppler velocimetry. Morris RK, Malin G, Robson SC, et al. Fetal umbilical artery Doppler to predict compromise of fetal/neonatal wellbeing in a high-risk population: systematic review and bivariate meta-analysis. Ultrasound Obstet Gynecol 2011; 37:135.
  56. Summary and recommendations-overview Evaluation and management of suspected fetal growth restriction (FGR) involves: Accurate determination of gestational age Confirming the diagnosis Distinguishing between the constitutionally small and the growth- restricted fetus onitoring the fetal weight trajectories Managing maternal comorbidities Serial assessment of fetal well-being Preterm delivery when indicated
  57. The more you give, the more you will get. Then life will become a sheer dance of love. H. H. Sri. Sri. Ravishankar The Art of Living Thank you

Editor's Notes

  1. Fetal growth restriction (FGR) is the final manifestation of a variety of maternal, fetal, and placental conditions. Fetal growth restriction occurs in up to 10% of pregnancies and is second to premature birth as a cause of infant morbidity and mortality. In addition to its significant perinatal impact, FGR also has an impact on long-term health outcomes. Fetal growth restriction remains a complex obstetric problem with disparate published diagnostic criteria, poor detection rates, and limited preventative and treatment options. 
  2. Limitations — The use of a percentile to define FGR is problematic because it does not distinguish among fetuses who are constitutionally small versus small because of a pathologic process that has kept them from achieving their genetic growth potential versus not small but kept from achieving their genetic growth potential by a pathologic process. As many as 70 percent of fetuses estimated to weigh below the 10th percentile for gestational age are small simply due to constitutional factors (eg, maternal ethnicity, parity, or body mass index) and are not at high risk of perinatal mortality and morbidity [13]. There is a real possibility of misclassifying these normally nourished, healthy, but constitutionally small, fetuses as growth restricted. By comparison, a malnourished fetus whose estimated weight is slightly greater than the 10th percentile may be misclassified as appropriately grown and at low risk of adverse perinatal outcome, even though its weight may be far below its genetic potential. A similar argument can be made when the AC is <10th percentile for the gestational age. An additional problem is that use of percentiles requires an appropriate reference, but there is little consensus on which reference should be used. Available references have been based on birth weights across gestation in a low-risk population (standard reference curve) or in an unselected population (population reference curve), on ultrasound-estimated fetal weights (EFW) across gestation, and on a customized standard [14,15]. The major flaw of birth weight reference standards is that infants who are born preterm are born early because of a pathologic process that often results in growth restriction. Ultrasound-based standards avoid this bias but are limited by the inaccuracy and imprecision of ultrasound-EFW.
  3. Limitations — The use of a percentile to define FGR is problematic because it does not distinguish among fetuses who are constitutionally small versus small because of a pathologic process that has kept them from achieving their genetic growth potential versus not small but kept from achieving their genetic growth potential by a pathologic process. As many as 70 percent of fetuses estimated to weigh below the 10th percentile for gestational age are small simply due to constitutional factors (eg, maternal ethnicity, parity, or body mass index) and are not at high risk of perinatal mortality and morbidity [13]. There is a real possibility of misclassifying these normally nourished, healthy, but constitutionally small, fetuses as growth restricted. By comparison, a malnourished fetus whose estimated weight is slightly greater than the 10th percentile may be misclassified as appropriately grown and at low risk of adverse perinatal outcome, even though its weight may be far below its genetic potential. A similar argument can be made when the AC is <10th percentile for the gestational age. An additional problem is that use of percentiles requires an appropriate reference, but there is little consensus on which reference should be used. Available references have been based on birth weights across gestation in a low-risk population (standard reference curve) or in an unselected population (population reference curve), on ultrasound-estimated fetal weights (EFW) across gestation, and on a customized standard [14,15]. The major flaw of birth weight reference standards is that infants who are born preterm are born early because of a pathologic process that often results in growth restriction. Ultrasound-based standards avoid this bias but are limited by the inaccuracy and imprecision of ultrasound-EFW.
  4. Classification — Regardless of the FGR definition used, FGR may be classified as early or late and as symmetric or asymmetric: ●Early FGR refers to diagnosis before 32 weeks of gestation, in the absence of congenital anomalies. ●Late FGR refers to diagnosis at ≥32 weeks of gestation, in the absence of congenital anomalies. ●Symmetric FGR comprises 20 to 30 percent of FGR and refers to a growth pattern in which all fetal organs are decreased proportionally due to global impairment of cellular hyperplasia early in gestation.  Symmetric FGR is thought to result from a pathologic process manifesting early in gestation. ●Asymmetric FGR comprises the remaining 70 to 80 percent of the FGR population and is characterized by a relatively greater decrease in abdominal size (eg, liver volume and subcutaneous fat tissue) than in head circumference.  Asymmetric fetal growth is thought to result from the capacity of the fetus to adapt to a pathologic environment late in gestation by redistributing blood flow in favor of vital organs (eg, brain, heart, placenta) at the expense of nonvital fetal organs (eg, abdominal viscera, lungs, skin, kidneys) [16,17]. Undoubtedly, some overlap exists between these two entities.
  5. Classification — Regardless of the FGR definition used, FGR may be classified as early or late and as symmetric or asymmetric: ●Early FGR refers to diagnosis before 32 weeks of gestation, in the absence of congenital anomalies. ●Late FGR refers to diagnosis at ≥32 weeks of gestation, in the absence of congenital anomalies. ●Symmetric FGR comprises 20 to 30 percent of FGR and refers to a growth pattern in which all fetal organs are decreased proportionally due to global impairment of cellular hyperplasia early in gestation.  Symmetric FGR is thought to result from a pathologic process manifesting early in gestation. ●Asymmetric FGR comprises the remaining 70 to 80 percent of the FGR population and is characterized by a relatively greater decrease in abdominal size (eg, liver volume and subcutaneous fat tissue) than in head circumference.  Asymmetric fetal growth is thought to result from the capacity of the fetus to adapt to a pathologic environment late in gestation by redistributing blood flow in favor of vital organs (eg, brain, heart, placenta) at the expense of nonvital fetal organs (eg, abdominal viscera, lungs, skin, kidneys) [16,17]. Undoubtedly, some overlap exists between these two entities.
  6. FGR: fetal growth restriction; EFW: estimated fetal weight; AC: abdominal circumference; NST: nonstress test; AFV: amniotic fluid volume; BPP: biophysical profile. * To assess FGR risk, refer to UpToDate content on causes and risk factors for FGR. Patients with multiple gestations or large or multiple leiomyomas and some patients with obesity are not appropriate candidates for measurement of the symphysis to top of the fundus distance alone because it does not correlate well with fetal size in these settings. ¶ The most common criterion for discordancy is a fundal height in centimeters that is at least 3 centimeters less than the gestational age in weeks. Alternatively, a fundal height measurement below the 10th percentile for gestational age can be used: The INTERGROWTH-21st Project International published printable symphysis-fundal height measurement standards for the 3rd, 10th, 50th, 90th, and 97th percentiles. Δ EFW or AC <10th percentile or oligohydramnios. ◊ The frequency of monitoring and use of additional types of monitoring (eg, ductus venosus) need to be individualized. The timing of delivery is based on a combination of factors, including gestational age, umbilical artery Doppler findings, BPP score, ductus venosus Doppler, and the presence or absence of risk factors for, or signs of, uteroplacental insufficiency. The goal is to maximize fetal maturity and growth while minimizing the risks of fetal or neonatal mortality and short-term and long-term morbidity. Refer to UpToDate content on evaluation and management of FGR. Graphic 131353 Version 1.0
  7. Fetal genetic studies – Fetal genetic studies are indicated in any of the following settings because of the increased risk of an abnormality: •FGR that is all of the following: Early (<24 weeks), severe (<5th percentile), and symmetrical. •FGR with major fetal structural abnormalities. •FGR with soft ultrasound markers associated with an increased risk of aneuploidy, such as thickened nuchal fold/choroid plexus cyst and abnormal hand positioning. (See "Prenatal genetic evaluation of the fetus with anomalies or soft markers", section on 'Approach to the evaluation of the fetus with "soft markers" and no structural anomalies'.) •Placental findings suggestive of a partial molar pregnancy: Enlarged, cystic spaces ("Swiss cheese pattern") and/or increased echogenicity of chorionic villi. The American College of Obstetricians and Gynecologists suggests genetic counseling and offering diagnostic testing for patients with diagnosis of FGR before 32 weeks or FGR in combination with polyhydramnios or fetal malformation [10]. Ultrasound examination has high sensitivity for identifying trisomy 18, as high as 100 percent, when performed by an experienced ultrasonographer at 19 to 20 weeks of gestation in a fetus with multiple structural anomalies characteristic of the syndrome. (See "Sonographic findings associated with fetal aneuploidy", section on 'Trisomy 18'.) If ultrasound examination strongly suggests trisomy 18 (positive predictive value depends on the number and types of ultrasound findings), we use a cell-free DNA test to screen for trisomy 18. If cell-free DNA testing is positive for trisomy 18 in this specific setting, we do not believe amniocentesis is essential to confirm the diagnosis. We counsel the patient regarding false positives and negatives and will perform amniocentesis for confirmation if the patient chooses this approach. In a 2016 meta-analysis, the positive predictive value of cell-free DNA for trisomy 18 in a general obstetric population and a high-risk population was 37 and 84 percent, respectively [11], and would be higher when associated with ultrasound findings characteristic of the syndrome. However, if a karyotype has not been obtained, it should be obtained for confirmation after delivery (or termination) to determine whether the trisomy was the result of a parental balanced translocation, as this will impact the recurrence risk in future pregnancies.  If cell-free DNA is negative for trisomy 18, we perform genetic amniocentesis to obtain amniocytes for microarray analysis; microarray has a significantly higher diagnostic yield than conventional karyotype [12]. The most common pathogenic copy number variants are 22q11.1 duplication, Xp22.3 deletion, and 7q11.23 deletion [13]. We use the same approach if ultrasound examination reveals abnormalities for which detailed genetic analysis is indicated.  In most clinical settings, the combination of positive cell-free DNA results and ultrasound findings do not provide sufficient diagnostic certainty to allow omission of fetal karyotype/microarray by genetic amniocentesis if pregnancy termination is planned because of suspected aneuploidy alone. In addition, a negative cell-free DNA test does not exclude the possibility of a pathogenic chromosome abnormality not targeted by the test but associated with FGR. (See "Sonographic findings associated with fetal aneuploidy", section on 'Trisomy 13' and "Prenatal diagnosis of chromosomal imbalance: Chromosomal microarray", section on 'Benefits compared with conventional karyotype'.) Although the finding of symmetrical FGR prior to 24 weeks of gestation is associated with a high risk of aneuploidy, this is no longer the case later in gestation [13]. After 24 weeks, we do not screen for fetal genetic abnormalities if anatomy is normal and FGR is asymmetric since the yield would be low, the etiology is most likely a maternal or placental disorder, and pregnancy termination is generally not an option. In a systematic review of 14 observational cohort studies including 874 apparently isolated FGR cases, the mean rate of chromosome anomalies was 6.4 percent (range 0 to 26 percent), and no abnormal karyotypes were found in the two studies of apparently isolated FGR diagnosed in the third trimester (32 pregnancies) [14].  FGR with a normal microarray could be due to a single gene disorder, particularly if FGR is severe (<1st percentile) and/or associated additional ultrasound findings (eg, short long bones; microcephaly; cardiac defects; relative macrocephaly; abnormalities of the face, hands, and/or genitalia). Gene panels and whole exome sequencing for evaluation of FGR have not been validated, have low diagnostic yield, and are not recommended [13]. However, testing for a single gene disorder is reasonable with appropriate pre- and post-test counseling in cases with high suspicion (eg, positive family history for a single gene disorder, skeletal dysplasia). Consultation with a genetics professional is advised. Most cases of confined placental mosaicism (CPM) do not result in FGR, but CPM is detected after delivery in approximately 10 percent of placentas associated with otherwise idiopathic FGR [15-17]. CPM is associated with an increased frequency of placental infarcts and decidual vasculopathy, presumably because some abnormal karyotypes can adversely affect placental function. In pregnancies complicated by FGR, approximately one-third of placentas with an infarct have underlying CPM [18]. We do not perform chorionic villus sampling in the second or third trimester to identify this abnormality antepartum because antenatal diagnosis would not change pregnancy management and the procedure is associated with a small risk of pregnancy complications. (See "Chorionic villus sampling", section on 'Confined placental mosaicism'.)
  8. The general sequence of Doppler and biophysical changes in FGR is:  ●A reduction in umbilical venous flow is the initial hemodynamic change. Venous flow is redistributed away from the fetal liver and towards the heart. Liver size decreases, causing a lag in fetal abdominal circumference, which is the first biometric sign of FGR. ●Umbilical artery Doppler index increases (diminished end-diastolic flow) due to increased resistance in the placental vasculature. ●Middle cerebral artery (MCA) Doppler index (eg, pulsatility index) decreases (increased end-diastolic flow), resulting in preferential perfusion of the brain (brain-sparing effect). ●Increasing placental vascular resistance results in absent and then reversed end-diastolic flow in the umbilical artery.  ●MCA peak systolic velocity increases secondary to an increase in the PCO2 and decrease in the PO2 in blood delivered to the fetal brain [31]. ●MCA pulsatility index (MCAPI) normalizes or abnormally increases as diastolic flow falls due to loss of brain-sparing hemodynamic changes.  ●As cardiac performance deteriorates due to chronic hypoxia and nutritional deprivation, absent or reversed end-diastolic flow in the ductus venosus and pulsatile umbilical venous flow may develop.  ●Lastly, tricuspid regurgitation and reversed flow at the aortic arch develop, which can be preterminal events. Near the end of this sequence, biophysical changes usually become apparent: The nonstress test (NST) becomes nonreactive, the BPP score falls, and late decelerations accompany contractions. However, the cardiovascular (Doppler) and behavioral (BPP) manifestations of fetal deterioration in FGR fetuses can occur largely independent of each other, resulting in discordant Doppler and BPP findings [32]. 
  9. These data suggest that delaying delivery of the very preterm growth-restricted fetus in the setting of uncertainty results in some stillbirths, but immediate delivery produces an almost equal number of neonatal deaths, and neither approach results in better long-term neurodevelopmental outcome. Although widely cited, these studies are difficult to evaluate due to the lack of standard criteria for intervention.
  10. The Disproportionate Intrauterine Growth Intervention Trial At Term trial (DIGITAT) randomly assigned 650 pregnant women over 36.0 weeks of gestation with suspected FGR to induction of labor or expectant monitoring [93-95]. The primary outcome was a composite measure of adverse neonatal outcome (death before hospital discharge, five-minute Apgar score <7, umbilical artery pH <7.05, or admission to the intensive care unit) [93]. Neonatal morbidity was analyzed separately using Morbidity Assessment Index for Newborns (MAIN) score [94]. The induction group delivered 10 days earlier and weighed 130 grams less (mean difference -130 grams, 95% CI -188 to -71) than the expectantly managed group, but had statistically similar composite adverse outcome (6.1 versus 5.3 percent with expectant management) and cesarean delivery rates (approximately 14 percent) [93]. Developmental and behavioral outcomes at two years of age were also similar for both groups [95]. The authors concluded that both approaches were reasonable, and the choice should depend on patient preference. However, in a subanalysis of the data, they also reported that neonatal admissions were lower when growth restricted fetuses were delivered after 38 weeks of gestation [94], which suggests a benefit of deferring delivery until 38 weeks of gestation, as long as the fetus is closely monitored and in the absence of other indications for an early delivery.
  11. TRUFFLE assessed whether changes in the fetal ductus venosus Doppler waveform could be used to guide timing of delivery of growth-restricted fetuses with a high umbilical artery Doppler pulsatility index (>95th percentile) instead of the conventional approach using cardiotocography short-term variation (STV) [49]. The primary outcome measure was survival without neurodevelopmental impairment at two years of age. Pregnancies were randomly assigned to one of three monitoring approaches: cardiotocography with delivery for reduced STV, ductus venosus monitoring with delivery for early ductus venosus changes (pulsatility index >95th percentile), or ductus venosus monitoring with delivery for late ductus venosus changes (a-wave indicating absent or reversed flow). The proportion of infants surviving without neurodevelopmental impairment was 77 to 85 percent, with no significant differences among the three groups. Among survivors, delaying delivery until the development of late ductus venosus changes resulted in an improvement in survival without neurodevelopmental impairment (95 percent versus 91 percent for the early ductus venosus changes group and 85 percent in the reduced STV group); however, this came at the cost of a small increase in unexpected fetal demise (0/166 in the STV group versus 3/167 in the early ductal changes group versus 4/170 in the late ductal changes group). There were no differences in immediate neonatal composite morbidity or mortality.  These findings do not support a change in clinical practice, given that the improvement in neurodevelopment was offset, in part, by an increase in fetal demise. Moreover, the number of neurodevelopmentally impaired children in each group was small (7 in the late ductal changes group, 12 in the early changes group, and 20 in the STV group); thus a larger trial may have resulted in a different outcome. Lastly, it is not clear that the investigators adjusted neurodevelopmental outcome scores for the mother's educational level.  In a post hoc analysis of their data, the TRUFFLE group concluded both ductus venosus and cardiotocography evaluation are warranted since the majority of infants in the ductus venous groups were delivered for reduced STV or spontaneous decelerations in fetal heart rate rather than early or late pulsatility changes in the ductus venous [96]. These observations clearly demonstrate the need for additional study of the most appropriate methods to determine delivery timing in the very preterm (<32 weeks of gestation) FGR fetus. 
  12. Longer term outcomes — An association has been observed between poor fetal growth, early accelerated postnatal growth, and later development of obesity, metabolic dysfunction, insulin sensitivity, type 2 diabetes, and cardiovascular and renal diseases (eg, coronary heart disease, hypertension, chronic kidney disease). This association has been attributed to partial resetting of fetal metabolic homeostasis and endocrine systems in response to in utero nutritional deprivation. The combination of prematurity and severe FGR increases the risk of long-term neurodevelopmental abnormalities and decreased cognitive performance. Numerous studies have also demonstrated fetal, neonatal, and long-term cardiac remodeling, which may be associated with cardiovascular morbidity and mortality later in life [114-117]. Concerns regarding an increased frequency of long-term metabolic and cardiovascular abnormalities raise the question whether preterm delivery may prevent these abnormalities. There are no data to support early delivery for this indication, but timing of delivery based on prevention of long-term morbidities related to impaired in utero growth needs careful study.
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