ANTEPARTUM FETAL MONITERINGProf. M.C.BansalMBBS., MS., FICOG., MICOG.Founder Principal & Controller,Jhalawar Medical College & Hospital Jjalawar.MGMC & Hospital , sitapura ., Jaipur
ANTEPARTUM FETAL MONITORING Two thirds of fetal deaths occur before the onset of labor, many of which are due to uteroplacental insufficiency. No single test can detect abn with 100% accuracy Ideal detection: allows intervention before fetal death or damage from asphyxia. Preferable: treat disease process and allow fetus to go to term. DRAWBACK- false positive / negative results may cause undue intervention and lead to premature iatrogenic delivery or fetal compromise.
METHODS OF ASSESSMENT•Assessment of Uterine growth•Fetal movement counting•Non stress test- indicator of fetal health.•Contraction stress test – indicator of U.P func.•Fetal Biophysical profile•Modified Biophysical profile•Doppler velocimetry•Percutaneous umbilical blood sampling
Occurs due to inadequate delivery of nutritive & respiratory substt to fetal tissues. Can be due to:-Inadequate exchange Maternal Fetal uptakewithin placenta due inadequacy to problemsto- deliver nutrients & oxygen through1. increased placentathickness2. reduced blood flow3. decreased sf area
SEQUENCE OF FETALDETERIORATION/COMPROMISEGeneralized Fetal Well Being with some Nutritional Compromise Fetal Growth Retardation with Marginal Placental Dysfunction Fetal Hypoxia under Stress cond. with Decreasing Respiratory Function Asphyxia/Death/Residual effects with Profound Respiratory Compromise
UTERINE GROWTH ASSESSMENTGeneral rule: Fundal height in centimeters = weeks ofgestation (2nd trim.)Johnson’s formula = [Ht. of uterus above symphysis (cm)– 12 (vx at or above ischial spines)OR 11 (vx below ischial spines)] x 155Exceptions: Maternal Obesity, MultipleGestation, Polyhydramnios, Abnormal FetalLie, Oligohydramnios, Low Fetal Station, and Fetal GrowthRestriction.Abnormalities of fundal height should lead to further
FETAL MOVEMENT COUNTINGMATERNAL PERCEPTION OF REDUCTION IN MOVEMENTS MAYBE A RED FLAG SIGN TO IMPENDING FETAL DISTRESS.
•4 fetal behaviour states as described by Nijhuis & colleagues (1982)based on fetal movements, fetal heart rate & eye movements :- 1. State 1F- Quiescent state- quiet sleep with narrow oscillatory bandwidth of fetal heart rate. 2. State 2F- Frequent gross body movements, cont. eye movements, wider oscillations of fetal heart rate. (=REM of neonate) 3. State 3F- Continuous eye movements in absence of body movements and heart rate accelerations. The existence of such state is doubtful 4. State 4F- Vigorous body movements with constt eye movements and heart rate accelerations.
USG observations show that fetus has gross body movementsapprox 10% of the time and as many as 30 movements can occur inan hour.Most commonly used method is “ COUNT TO 10” (Moore et all 1989) [Am J Obs-Gyn]Patients are instructed to count until they reach 10 movements.If such 10 movements are noticed in 10 hours, most probably thefetus is in good health. (1 movement in each hour).If mother reports <10 movements in 10 hours OR there is doublingof hours usually required to complete 10 movements, she should besubjected to further evaluation.
• Studies have indicated a good correlation b/w fetal movementsperceived by the mother and those picked on a real time scan.• Periods of fetal activity lasts for about 40 mins and that of restabout 20 mins. The mother usually perceives 70-80% of thesemovements.• Passive fetal movements begin by about 7wks and become morecoordinated towards end of pregnancy. (Vindla and James 1995)• Beyond 8 wks, body movements are never absent for periodsexceeding 13 minutes. (De Vries and co workers 1985)•Between 20-30 wks, general body movements become organised andfetus starts to show „rest-activity cycles‟. (Sorokin and co-workers 1982)
FACTORS AFFECTING PERCEPTION OF MOVEMENTS Maternal obesity Excessive liquor Placental site (?) Fetal malformations
oMost commonly used test. The patient placed in semifowler‟s position.oNon invasive, easy to perform, interpret and readilyaccepted by patients.oTest looks for presence of fetal heart rate (FHR)accelerations associated with fetal movements.oThis reflex involves the cerebral cortex, and is affectedby physiological (fetal sleep) or pathological influences(fetal hypoxia) on fetal brain.
•Two normal patterns of NST are:- a. Reactive - 2/more accelerations of FHR of min 15 beats/min, lasting for atleast 15 secs from baseline to baseline within 20 mins obsv pd, associated with fetal movements (as perceived by the mother).
b. Non Reactive- Lack of such accelerations for a pd of 40 mins. (20 mins as per normal obsv pd + additional 20 mins)
Introduced by Zimmer et all, 1993.Stimulation via an artificial larynx, over the fetal head along withNST attached & producing vibratory acoustic stimulus of approx 80Hzand 82dB.A healthy fetus responds with a sudden movement (StartleResponse) followed by FHR acceleration.Response to VAS is gestational age dependant, viz, a fetus of lessthan 24 wks doesn‟t respond to it.Between :-24-27wks 30% 27-30wks 86% fetuses will respond to the stimulus. >31wks 90%
NST is to be read keeping in account all the variables namely, 1. Baseline FHR 2. Variability of FHR 3. Presence /absence of decelerations 4. Presence /absence of accelerationseach one being separately analysed. Normal baseline FHR IS 110-160 bpm. >160 is tachycardia & <110 is bradycardia. Variability is the most imp parameter to be read and interpreted. Itdepends upon interactions of fetal sympathetic & parasympatheticnervous systems.It‟s influenced by gestational age, fetal tachycardia, maternalmedications, congenital anomalies and fetal acidosis. A non reactive NST in presence of variability suggests a false positivereading
drawbacks•Can‟t pick up early fetal compromise. Though, this concern hasn‟t beenproven in clinical trials and hasn‟t effected the use of NST as a primary toolfor diagnosis.•Use of test alone without realising the significance of other tests which maybe better for the given patient. Eg. In postdated pregnancies, simultnassessment of amniotic fluid volume is necessary.(Kontopoulos and Vintzileos, 2004)•Gandhi (2003), emphasised that though false positive rate ranges between65-70%.•A cumulative view of 50,000 cases (Ware and Devoe, 1994) revealed aperinatal mortality of 6.2/1000.He also states that diagnostic value of NST remains as good as CST and issimpler to perform.
Based on experimental evidence showing thatuteroplacental blood flow decreases markedly or ceasesduring each uterine contraction. Thus, uterinecontractions cause a hypoxic state that a normal, healthyfetus can tolerate without difficulty.In contrast, fetus with acute/chronic problems will not beable to tolerate such a decrease in oxygen supply & willdemonstrate decelerations of FHR following contraction.Contractions can be- a. spontaneously occuring b. induced with oxytocin drip ( predictable response) c. nipple stimulation (unpredictable response)
HOW TO PERFORM CST1. Patient on semi fowler‟s position.2. Tocographic equipment applied to maternal abdomen, observe uterine activity with FHR variations every 15-20 mins. Spontaneous contractions present in many cases. If not induction of contractions may be necessitated.3. Start IV oxytocin at 0.5 mU/minute, using pump. Double the rate every 15- 20 mins till 3 contractions, of 40-60 secs occur within 10 mins time. Amount required to achieve adequate contractions usually below 16 mU/ml. Alternately, warm towel can be used to stimulate the nipples.4. After completion uterine contractions and FHR should be monitered till they return to baseline. If not, subcutn admin of 250 mg of terbutaline reqd to paralyze the uterus.
End point of CST is presence or absence of decelerations of FHR withuterine contractions.Late decelerations are one of the earliest indicators of fetal compromise &appear due to loss of variability, decreased movement, loss of tone.The test is infrequently used due to:- 1. long obsv periods by trained professionals. 2. risks and contraindications.*Positive: presence of late decelerations with at least 50% of thecontractions*Negative: no late or significant variable decelerations*Equivocal—Suspicious: presence of late decelerations with fewer than50% of contractions) or significant variable decelerations*Equivocal—Tachysystole: Presence of contractions that occur morefrequently than every 2 minutes or last longer than 90 seconds in thepresence of late decelerations*Equivocal—Unsatisfactory: Fewer than three contractions occur within10 minutes, or a tracing quality that cannot be interpreted
CONTRAINDICATIONS1. Placenta praevia2. Prior classical cesarean section3. Prior extensive uterine surgery4. Preterm labour / High risk of preterm labour5. PROM6. Incompetent os
A. Negative CST. Absenceof late decelerations, oftenoccasional accelerations.B. Positive CST. Recurrentuniform late decelerationspresent.C. CST. Variabledecelerations present.D. Hyperstimulation.Prolonged contraction withreflexive deceleration.
Positive CST conveys the strong possibility that placental respiratoryinsufficiency is present, although it does not indicate the probable durationor progress of this condition.In addition, the positive CST conveys much higher risk of fetal distress, low5-minute Apgar scores, and IUGR than does a negative test. Devoe, L, Glob. libr. womens med., (ISSN: 1756-2228) 2008; DOI 10.3843/GLOWM.10210
Combines NST with ultrasound assessment of 4 variables.5 parameters are-•Fetal Breathing Movements- 30 secs sustained movmnt in 30 minsobsv.•Fetal Movement- 3/more gross body movements in 30 mins obsv•Fetal Tone- 1/ more movement from flexion to extension andreturn to flexion.•FHR reactivity- 2/more accelerations of 15bpm, lasting atleast 15secs.•Fluid Volume- at least 2 pockets meas. 2cm in 2 perpendicularplanes.Variables are dependant on integrity of fetal CNS & are affected in fetalcompromise.
Each parameter assigned points-- 2 if present/normal. 0 if absent/abnormal.A BPP normally is not performed before the second half of a pregnancy, sincefetal breathing movements do not occur in the first half.A BPP of 8 or 10 is generally considered reassuring, as long as score of 8doesn‟t include abnormal fluid volume.PRESENCE OF OLIGOHYDRAMNIOS DEMANDS FURTHER TESTINGNO MATTER WHAT THE SCORE IS.A score of 6 is Equivocal and requires further testing to verify findings.A score of 4/less suggests fetal compromise.
BPP variables are dependant on fetal CNS development acc togestational age.Fetal tone & movement appear b/w 7-9 wks and require activity of braincortex.Fetal breathing movements begin at 20-21 wks & depend on centres on ventralsurface of 4th ventricle.FHR reactivity appears b/w 28-30 wks & controlled by posthypothalamus, upper medulla.Sensitivity of each centre to hypoxia is different & ones which develop earlierare more resistant to effects of fetal hypoxia.First manifestation of fetal acidosis- nonreactive NST, lack of fetal breathingmovements. Decreased body movements and loss of tone occur with severecompromise.
Vintzileos et al (1987) , Clark et al (1989), Miller et al (1996) Excellent test for primary fetal surveillance.Combines use of NST with VAS, and Amniotic Fluid IndexTest has:- excellent positive & negative predictive values easy to interpret clearly defined end points average time needed is 20 mins
Following guidelines are useful while reading the results:-1. Both NST and AFI are normal, cont weekly fetal monitoring.2. Both tests abnormal; a) >36 wks, best option is delivery b) <36 wks, individualized treatment3. NST reactive, but AFI low, search for causes of UPI or undiagnosed ROM.4. AFI normal, but NST non reactive, further testing with Doppler, CST, BPP.
*Non invasive technique to assess placental blood flow to the fetus.*Uses waveforms to describe Systolic (S) & Diastolic (D) blood flow throughvessels. S D *Three commonly used ratios are:- a. S/D Ratio b. S-D/S = Resistance Index c. S-D/Mean = Pulsatility Index
Acc to Trudinger (2007); >40% of total fetal ventricular output directed to placenta obliteration of utero placental circulation increases afterload further hypoxia dilatation & redistribution of MCA blood flow pressure rises in Ductus Venosus due to increased afterload to right side of fetal heart
•Vessel normally has forward flow throughout cardiac cycle & diastolic flowincreases as gestation advances.•So, S/D ratio decreases as gestation advances, from 4 at 20 wks to <3by 30 wks & finally 2 at term.•S/D ratio is taken as abnormal if it‟s above 95th percentile forgestational age OR diastolic flow is absent or reversed.•A resistance index > 0.72 is greater than the normal limits from 26 weeksgestation onwards.
• Abnormal waveforms can be present for weeks before there is evidence offetal compromise.These are a marker of a high risk situation and should not normally be usedin isolation as an indication for delivery.•Most would consider delivering a fetus with absent end-diastolicvelocity from about thirty two weeks gestation followingadministration of corticosteroids.•However, reversal of end diastolic blood flow is an ominous sign &predicts severe fetal compromise, possible death, requiring urgentdelivery of the viable fetus.
Konjoe & colleagues (2001) [Br J of Obs & Gyn]Doppler studies of MCA showed, hypoxic fetii attempt brain sparing byreducing cerebrovascular impedance & thus reducing blood flow. In growth restricted fetii this effect shows reversal.The effect however, isn‟t protective, rather indicates negatively on the fetalhealth.
INCREASED DIASTOLICFLOW, due to reduced resistance.NORMAL doppler flowHighly reduced resistance, shown byFURTHER INCREASE OFDIASTOLIC FLOW.REVERSAL OF DIASTOLICFLOW, indicative of severe fetalcompromise.
•F. Daffos (1983-1985)•22 G / Finer needle needed.•Can be performed at any site on umbilical cord, but placental insertionpreferred.•One should avoid piercing through the placenta.
INDICATIONSa) Rapid Karyotype In Fetuses Detected With Anomalies On USG.b) Fetal Hemolytic Diseasec) Suspected Fetal Viral Infectiond) Non Immunologic Hydrops Fetalise) Suspected Fetal Thrombocytopeniaf) Twin To Twin Transfusiong) Fetal Heamoglobinopathies
RISKS BLEEDING FROM PUNCTURE SITEVASO VAGAL REFLEXFETAL BRADYCARDIA
Ideally an obstetrician should adequately inform the patient of allthe pros and cons of any test method being employed, and theefficacy and limitations of the same.In many instances, failing to do so, may cause the patient to haveunreasonable expectations which when unfulfilled may lead toanimosity and disappointment towards the doctor and causemedico-legal problems
SOURCES1. WILLIAMS TEXTBOOK OF OBSTETRICS 23RD EDITION.2. PRACTICAL BOOK TO HIGH RISK PREGNANCY 3RD EDITION by FERNANDO ARIAS.