pregnancy dating, assessment gesational age

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accurate assessment of gestational age by certain mensrtual data and clinical examination may have dating discrepancy with the ultrasound. this ppt critically addresses such issues

accurate assessment of gestational age by certain mensrtual data and clinical examination may have dating discrepancy with the ultrasound. this ppt critically addresses such issues

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  • 1. veerendrakumarcm@gmail.com
  • 2. Importance of reliable pregnancy dating:  Appropriate timing of gestational age-related testing  Avoid iatrogenic newborn prematurity  Decisions regarding delivery timing and treatment of PTL or PPROM  Determine when to initiate post term fetal surveillance2/15/2013 10:00 AM/ dr.veerendrakumar cm 2
  • 3.  Pregnancy dating methods  Pitfalls  Dating discrepancy  Judicious use of technology for better outcome  Learn to critically analyze dating !!!2/15/2013 10:00 AM/ dr.veerendrakumar cm 3
  • 4.  Social and medical significance  Time frame around which many activities are planned2/15/2013 10:00 AM/ dr.veerendrakumar cm 4
  • 5.  when dates are inaccurate, antenatal test results will be incorrect and misleading. Cowchock FS, Clin Obstet Gynecol 19: 871, 19762/15/2013 10:00 AM/ dr.veerendrakumar cm 5
  • 6. Obstetric management is dependent on gestational ageGoldenberg RL, Am J Obstet Gynecol 123: 617, 19752/15/2013 10:00 AM/ dr.veerendrakumar cm 6
  • 7. Elephant- 640 daysDogs- 63 daysCat- 65 daysMonkey- 164 daysMouse- 21 daysSheep- 150 daysCow- 280 daysHuman- 266 days
  • 8. DO WE MATURE EARLY?  Does gestation vary by ethnic group? A London-based study of over 122 000 pregnancies with spontaneous onset of labour Roshni R Patel, Philip Steer, I J E VOL 33 No.1 107-113 ,20042/15/2013 10:00 AM/ dr.veerendrakumar cm 8
  • 9. Metabolic nirvana ….  The median gestational age at delivery was 39 weeks in Blacks and Asians and 40 weeks in white Europeans.  Meconium stained amniotic fluid, which is a sign of fetal maturity, was statistically significantly more frequent in Black and Asian infants compared with white European infants.2/15/2013 10:00 AM/ dr.veerendrakumar cm 9
  • 10. The age… 1.Menstrual age 2.Gestational age 3.Embryological age 1 22 32/15/2013 10:00 AM/ dr.veerendrakumar cm 10
  • 11. Basic methods  Menstrual history  Clinical examination  Ultrasound examination2/15/2013 10:00 AM/ dr.veerendrakumar cm 11
  • 12. Menstrual history  Indirect measure of conception of roughly 280 days  Reliability depends and influenced by - recall of memory - presence of light bleeding - regularity of cycles - OCP, breast feeding etc Nichols C. Dating pregnancy. J Nurse Midwifery. 1987;32:195-204. cm2/15/2013 10:00 AM/ dr.veerendrakumar 12
  • 13. Menstrual age  Overestimates the gestational age Wilcox M et al BMJ 1993;307(6904):588-91  10-45% do not provide correct information  18% with certain dates have significant difference with USG age Geirsson et al, Br J Obstet Gynaecol. Jan 1991;98(1):108-9.2/15/2013 10:00 AM/ dr.veerendrakumar cm 13
  • 14. Naegeles’ rule does not correlate with actual conception date…. Baird et al 498 normal cycles luteal phase 7-19 days 10% ovulate on D14 Wicox et al only 30% of normal cycle women are fertile between 10-17 days2/15/2013 10:00 AM/ dr.veerendrakumar cm 14
  • 15. Reliable information on 1st day of LMP notequivalent with reliable information aboutthe start of pregnancy
  • 16. Naegeles revisited..  19th century Frederiech Naegele original article in German textbook  Naegele himself credits Harmann Boerhaave with Inventing the formula for EDD.  Its unclear whether 1st day of LMP or last day of LMP to be considered for EDD.2/15/2013 10:00 AM/ dr.veerendrakumar cm 16
  • 17. Other methods  Prem’s rule –based on BBT 7days subtracted from 1st day of thermal shift and 9 months added  M G Hiremath (KIMS Hubli) pt is ignorant about English calendar doctor is ignorant about Lunar calendar!  Paper presented- International Conference on labour and delivery at Mumbai 1994.2/15/2013 10:00 AM/ dr.veerendrakumar cm 17
  • 18. 2/15/2013 10:00 AM/ dr.veerendrakumar cm 18
  • 19. Time to discard Naegele’s?  Error prone EDD not acceptable in modern times Katz VL et al Why we should eliminate the due date: A truth in jest. Obstet Gynecol. 2001;98:1127-1129 Gardosi J. Dating of pregnancy: Time to forget the last menstrual period. Ultrasound Obstet Gynecol. 1997;9:367- 368 Savitz DA. Comparison of pregnancy dating by last menstrual period, ultrasound scanning and their combination. Am J Obstet Gynecol. 2002;187:1660-16662/15/2013 10:00 AM/ dr.veerendrakumar cm 19
  • 20. That too when we know the embryolike this2/15/2013 10:00 AM/ dr.veerendrakumar cm 20
  • 21. 2/15/2013 10:00 AM29/12/2009 dr.veerendrakumar cm 21
  • 22. Ultrasound dating  RADIUS trial 1993 - 15,000 low risk women no clinical benefit to justify routine ultrasound in the absence of medical indications ACOG 2008 states that obstetricians are under no obligation to perform routine ultrasounds in low-risk women; however, it is reasonable to honor a patients request for one.!! Ultrasonography in pregnancy. Obstet Gynecol. 2008;112:951-962.2/15/2013 10:00 AM/ dr.veerendrakumar cm 22
  • 23. Obstetric ultrasound turned intoUltrasonic obstetrics Sono obstetrician2/15/2013 10:00 AM/ dr.veerendrakumar cm 23
  • 24. RADIOLOGIST CAN SURVIVE WITHOUT SCAN BUT NOT THE OBSTETRICIAN2/15/2013 10:00 AM dr.veerendrakumar cm 24
  • 25. All said …  Ultrasound examination of the fetus provides the most precise assessment of gestational age, especially in the first trimester. Callen USG in Obst and Gynecol 2008 ACOG PRACTICE BULLETIN 20082/15/2013 10:00 AM/ dr.veerendrakumar cm 25
  • 26. 9 RCT, > 34,000 women  Routine USG More accurate estimation of EDD earlier detection of twin pregnancies Neilson JP , Cochrane Database –Syst Review 2000 improved clinical management of parturient women2/15/2013 10:00 AM/ dr.veerendrakumar cm 26
  • 27.  inaccuracies of history and physical examination may limit their usefulness in assessment of gestational age.2/15/2013 10:00 AM/ dr.veerendrakumar cm 27
  • 28. • In vitro fertilization the most accurate means of predicting gestational age ( 1 day).  in most pregnancies, the date of ovulation or conception cannot be accurately predicted and gestational age must be established by other methods.2/15/2013 10:00 AM/ dr.veerendrakumar cm 28
  • 29. Methods of determining thegestational age  Parameter variability 2SD IVF 1 day Ovulation 3 days IUI 3 days Single I/C 4 days 1st trimester examn 2 weeks 2nd trimester examn 4 weeks 3rd trimester examn 6 weeks Callen PW. Ultrasonography in obstetrics and gynecology. 5th ed. Saunders Elsevier; 2008;p. 3-25.2/15/2013 10:00 AM/ dr.veerendrakumar cm 29
  • 30. Methods of determining the gestational age  Parameter Variability 2SD 1st trimester USG –CRL ± 8% of the estimate 2nd trimester USG –HC,FL ± 8% of the estimate 3rd trimester USG – HC,FL ± 8% of the estimate Callen PW. Ultrasonography in obstetrics and gynecology. 5th ed. Saunders Elsevier; 2008;p. 3-25.2/15/2013 10:00 AM/ dr.veerendrakumar cm 30
  • 31. USG technology evolved..  The margin of error is consistently ±8% by esteemed researchers Hadlock FP, Radiology. 1992;182:501-505 Doubilet ,J Ultrasound Med.1993;12:647-653 Taipale P, Obstet Gynecol. 2001;97:189-942/15/2013 10:00 AM/ dr.veerendrakumar cm 31
  • 32. In the first trimester  MSD and CRL- primary means of evaluating gestational age. Am J Obstet Gynecol 103: 789, 1969 Acta Obstet Gynecol Scand 50 (suppl): 29, 1971 Br J Obstet Gynaecol 82: 702, 19752/15/2013 10:00 AM/ dr.veerendrakumar cm 32
  • 33. Usg in First trimester  Gestational Sac (GS) - MSD used till embryo appears  add 30 to GS size in mm to get age in days2/15/2013 10:00 AM/ dr.veerendrakumar cm 33
  • 34. The sac is measured inside the hyperechoicrim, including only the echo-free space.2/15/2013 10:00 AM/ dr.veerendrakumar cm 34
  • 35. measurement of the fetal length from thetip of the cephalic pole to the tip of thecaudal pole.  The embryo is measured along its longest axis to obtain the CRL measurement accurately date pregnancy between 7 and 13 weeks gestation.  The fetus should be at rest and assuming its natural curvature.2/15/2013 10:00 AM/ dr.veerendrakumar cm 35
  • 36. CRL2/15/2013 10:00 AM/ dr.veerendrakumar cm 36
  • 37. Technical factors can lead toerrors in CRL measurements. - incorporation of the yolk sac or lower limbs in the CRL measurement, - excessive curling or extension of the fetus, - tangential section of the trunk. Robinson HP, A critical evaluation of sonar “crown- rump length” measurements. Br J Obstet Gynaecol 82: 702, 19752/15/2013 10:00 AM/ dr.veerendrakumar cm 37
  • 38. Overestimation… 17 mm- 8 weeks 22 mm -8 wks 5 days2/15/2013 10:00 AM/ dr.veerendrakumar cm 38
  • 39. Excessive flexion -underestimation 54 mm- 11wks 4 days 62mm- 12wks 4days 2/15/2013 10:00 AM29/12/2009 dr.veerendrakumar cm 39
  • 40.  The BPD is imaged in the transaxial plane of the fetal head at the level of thalami in the midline, equidistant from the temporoparietal bones and usually the cavum septum pellucidum anteriorly.  Linear correlation with BPD, HC racial difference with FL, not with HC GA (DAYS) =dr.veerendrakumar cm (BPD)in mm 39.1 + 2.12/15/2013 10:00 AM/ 40
  • 41. 2/15/2013 10:00 AM/ dr.veerendrakumar cm 41
  • 42.  Between 12 and 26 weeks the BPD is accurate ±10 to 11 days.  After 26 weeks the accuracy of BPD measurement progressively decreases and is ±3 weeks near term.2/15/2013 10:00 AM/ dr.veerendrakumar cm 42
  • 43.  BPD measurement is most accurate in assessing gestational age when the head shape is appropriately ovoid.  If the head is rounded (brachycephalic) or elongated (dolicocephalic), BPD measurements would overestimate or underestimate gestational age, respectively.  in fetuses with abnormal head shape, either brachycephaly or dolicocephaly, HC may be a more accurate predictor of fetal age than BPD. Hadlock FP, : Fetal head circumference: Relation to menstrual age. AJR 138: 649, 19822/15/2013 10:00 AM/ dr.veerendrakumar cm 43
  • 44. Technical factorsinfluence the accuracy.  Inter observer error, different techniques of measurements, and single versus multiple measurements The limitations of ultrasonic fetal cephalometry. J Obstet Gynaecol Br Commonw 80: 769, 1981 2/15/2013 10:00 AM/ dr.veerendrakumar cm 44
  • 45. AC is obtained..  in the trans axial view of the fetal abdomen, at the level of the fetal liver, the umbilical portion of the left portal vein & fetal stomach which is at the same level2/15/2013 10:00 AM/ dr.veerendrakumar cm 45
  • 46. 2/15/2013 10:00 AM/ dr.veerendrakumar cm 46
  • 47. AC is less accurate than headmeasurements (BPD or HC).  AC is the growth parameter most commonly affected in pregnancies complicated by abnormal fetal growth patterns.  Hadlock FP, Deter RL, Harrist RB, Park SK: Fetal abdominal circumference as a predictor of menstrual age. AJR 139: 367, 19822/15/2013 10:00 AM/ dr.veerendrakumar cm 47
  • 48. GASA and Multiple parameters  To improve the accuracy of gest age- assessment growth-adjusted sonographic age ( GASA) and averaging multiple parameters are used. Sabbagha RE, GASA: A simplified method. Obstet Gynecol 51: 383, 1978 Hadlock FP, Am J Obstet Gynecol 156: 955, 19872/15/2013 10:00 AM/ dr.veerendrakumar cm 48
  • 49.  Gestational age can be more accurately predicted by obtaining paired BPD measurements  (the first from 20 to 26 weeks gestation and the second from 31 to 33 weeks gestation)  and assigning gestational age by a method known as growth-adjusted sonographic age (GASA).2/15/2013 10:00 AM/ dr.veerendrakumar cm 49
  • 50.  Use of GASA based on specific cephalic growth pattern increases the accuracy of gestation by BPD measurement to within ±3 to 5 days. Obstet Gynecol 51: 383, 19782/15/2013 10:00 AM/ dr.veerendrakumar cm 50
  • 51. Femur length  The largest of the long bones, least moveable, and easiest to image.  The ultrasound beam should be perpendicular to the shaft.  The measured ends should be blunt in appearance and the distal femoral epiphysis should not be included.2/15/2013 10:00 AM/ dr.veerendrakumar cm 51
  • 52. 2/15/2013 10:00 AM/ dr.veerendrakumar cm 52
  • 53.  FL accurately predict gestational age between 14 weeks and term.  Jeanty P, J Ultrasound Med 3: 75, 19842/15/2013 10:00 AM/ dr.veerendrakumar cm 53
  • 54. Biologic and technical factors may lead toinaccuracies of FL measurements. Overestimation of FL, particularly when the femur is in the far field or lateral margins of image.  Tangential section of the femur, failing to visualize the entire length of the shaft, leads to underestimation of FL2/15/2013 10:00 AM/ dr.veerendrakumar cm 54
  • 55.  The distal femoral epiphysis becomes echogenic in the third trimester, Inclusion of the distal epiphysis will falsely overestimate FL. Goldstein RB, Filly RA, Simpson G: Pitfalls in femur length measurements. J Ultrasound Med 6: 203, 19872/15/2013 10:00 AM/ dr.veerendrakumar cm 55
  • 56. The FL/BPD ratio (normal 79 ± 6%)  useful as an internal verification of the measurements obtained. Abnormal ratio is an indicator of pathologic entities,  Microcephaly ( abnormally high)  hydrocephalus or short-limb dysplasia (abnormally low).2/15/2013 10:00 AM/ dr.veerendrakumar cm 56
  • 57. Multiple Fetal GrowthParameters  If the gestational age estimates derived from all of the parameters are similar, assignment of gestational age from the average of all the parameters will improve accuracy.  If gestational age estimates of the various parameters are quite different, averaging multiple parameters will decrease the accuracy of the best predictor(s).2/15/2013 10:00 AM/ dr.veerendrakumar cm 57
  • 58. Averaging of fetal growth parametersshould be avoided  fetal macrosomia,  intrauterine growth retardation (both symmetric and asymmetric),  congenital anomalies (skeletal dysplasia, hydrocephalus and others)2/15/2013 10:00 AM/ dr.veerendrakumar cm 58
  • 59.  Assessment of gestational age is fundamental to obstetric care and should be a carefully thought-out process. Assessment should depend on history and physical examination, as well as ultrasound evaluation. Ultrasound is a reliable method for establishing the length of pregnancy and in this way can improve obstetric care.2/15/2013 10:00 AM/ dr.veerendrakumar cm 59
  • 60. SCAN IS A WONDERFULINSTRUMENT IN THE RIGHT HANDS2/15/2013 10:00 AM/ dr.veerendrakumar cm 60
  • 61.  an ultrasound performed before 24 weeks gestation establishes a more accurate EDD than relying solely on the LMP. Hadlock et al, Mongelli et al2/15/2013 10:00 AM/ dr.veerendrakumar cm 61
  • 62. Despite RADIUS….  In study of 17,000 women With reliable LMP dating post term delivery rate reduced from 10.3% to 2.7% Taipale P, Hiilesmaa V. Predicting delivery date by ultrasound and last menstrual period in early gestation. Obstet Gynecol. 2001;97:189-194.2/15/2013 10:00 AM/ dr.veerendrakumar cm 62
  • 63. Dating discrepancy  Problem arises in (busy) clinical practice when significant difference exist between due date calculated by LMP and USG especially when earlier scan is not done and patient presents late in pregnancy.2/15/2013 10:00 AM/ dr.veerendrakumar cm 63
  • 64. Ultrasound biometry ‘approximation of assumption’  In early pregnancy all fetuses of same age are of same size ! Variation increases with increase in gestational age  In late pregnancy different fetuses of same age are of different sizes2/15/2013 10:00 AM/ dr.veerendrakumar cm 64
  • 65. Reassigning the due date  ACOG recommends reassigning the date when difference exist between LMP & USG date. >7days difference up to 12 weeks > 10 days difference 12-20 weeks What about after 20 weeks?2/15/2013 10:00 AM/ dr.veerendrakumar cm 65
  • 66. Redating..2/15/2013 10:00 AM/ dr.veerendrakumar cm 66
  • 67. 2/15/2013 10:00 AM/ dr.veerendrakumar cm 67
  • 68. Man or machine? Or.. Middle path2/15/2013 10:00 AM/ dr.veerendrakumar cm 68
  • 69. The classical understanding…  1st trimester ± 1 week 2nd trimester ± 2 weeks 3rd trimester ± 3 weeks2/15/2013 10:00 AM/ dr.veerendrakumar cm 69
  • 70. Rule of 8  Hadlock regression analysis USG gestational age estimation is consistently accurate with 8% margin of error irrespective of the GA. This SD is to be converted into days’ gestation Hadlock F. Sonographic estimation of fetal age and weight. Radiol Clin North Am. 1990;28:39-50.2/15/2013 10:00 AM/ dr.veerendrakumar cm 70
  • 71. ±8 % variance (Hadlock) of theestimated gestational age not in weeks but convert into days! 8weeks = 56 days » 8% = 5 days 24 weeks =146 days » 8%=12 days 36weeks = 252 days » 8% = 20 days2/15/2013 10:00 AM/ dr.veerendrakumar cm 71
  • 72. The problem..  LMP 10/01/03 EDD 17/10/03 USG done on 1/9/03 gest age of 29 weeks 6day EDD 10/11/03  Difference is 24 days ! which one to consider?2/15/2013 10:00 AM/ dr.veerendrakumar cm 72
  • 73.  If difference is more than MOE -use USG EDD  If MOE is more than difference use LMP EDD2/15/2013 10:00 AM/ dr.veerendrakumar cm 73
  • 74.  Convert gestational age into days 29wks 6day = 209 days 8% of Margin of error (MOE) = 209 x 0.08 = 16.7 = 17 days final EDD is 10/11/032/15/2013 10:00 AM/ dr.veerendrakumar cm 74
  • 75. The baby was born on 2/11/20032/15/2013 10:00 AM/ dr.veerendrakumar cm 75
  • 76.  Use always earliest USG report  Subsequent USGs can be used to rule out developmental abnormalities.  Uniformity among obstetric providers without divergent opinion in arriving at Final EDD  Busy tertiary care hospital consistency is crucial  Allows residents to learn critically learn & examine the dating criteria  Evidence based management with confidence2/15/2013 10:00 AM/ dr.veerendrakumar cm 76
  • 77. 2/15/2013 10:00 AM/ dr.veerendrakumar cm 77