Outpatient Antenatal Testing FLAME LECTURE: 54 STELLER

Learning Objectives  Understand the rationale for prenatal outpatient fetal assessment  Describe approaches for assessment of fetal well being  Prerequisites:  FLAME LECTURE 53: Overview of Interpreting Fetal Heart Rate Tracings  See also – for closely related topics  FLAME LECTURE 54B: The Nonstress Test (NST) and Contraction Stress Test (CST)  FLAME LECTURE 56: The Biophysical profile  FLAME LECTURE 57: Assessment of fetal movement  FLAME LECTURE 59: Assessment of amniotic fluid volume

Rationale of Prenatal Outpatient Fetal Assessment  Goals  Detect uteroplacental insufficiency  Prevent stillbirth  Avoid unnecessary iatrogenic preterm delivery  Physiologic basis: The fetal brain is incredibly sensitive to changes in O 2 and pH, and under stress:  Chemoreceptor response to acidemia [ vagally-mediated deceleration of the fetal heart rate  Fetal movements decrease as the fetus attempts to conserve energy 1-2  Blood flow is directed to the brain, heart and adrenals and away from the kidneys [ a decrease in renal perfusion [ a decrease in fetal urine production [ oligohydramnios 1.Olesen AG. Acta Obstet Gynecol Scand Manning FA. AJOG 1993

Antepartum Fetal Distress Cascade HYPOXIAHYPOXIA ACIDOSISACIDOSIS LATE DECELERATIONS APPEAR (CST) ACCELERATIONS DISAPPEAR (NST) BREATHING STOPS (BPP) MOVEMENT CEASES (BPP, FMC) FETAL TONE ABSENT (BPP) Porto, Clin Ob Gyn, 1987

Antenatal Assessment Modalities  Fetal movement (kick) counting  Nonstress test  Contraction stress test  Biophysical profile (BPP) parameters: fetal breathing, fetal body movements, fetal tone, amniotic fluid volume  Modified BPP (mBPP) = NST + AFI  Umbilical Artery Doppler velocimetry (for IUGR fetuses only)

Indications for Antenatal Testing = Risk factors for uteroplacental insufficiency  Maternal  APL syndrome, SLE  Grave’s disease  Asthma, poorly controlled  Hemoglobinopathies  Cyanotic heart disease  Chronic renal disease  Type I DM, Type II DM  Hypertensive disorders  AMA (usually > 38 y.o.)  Pregnancy   Fetal movement  gHTN, Pre-eclampsia  A2 GDM  Oligohydramnios/ Poly  IUGR  Late-term/Post-term  Isoimmunization  Previous unexplained fetal demise  Monochorionic or discordant twins  Third trimester vaginal bleeding

Timing of antepartum surveillance  WHEN TO START?  WHY TO START?  HOW OFTEN TO PERFORM?  No large clinical trials to guide recommendations of initiation and frequency of testing

THE UCI APPROACH - Initiation 26 wks32 - DxIndividualize DM: DFR Htn IUGR Diabetes: Class BC Gestation Diabetes Post DatesPIHDecrease FM cHTN, SLE Immune disorders IUGRRh Isoimmun Antiphos- pholipid antibody syndrome Cardiac, pulmonary or renal disease Discord. Twins Mono-mono twins Mono-di twins Third trimester bleeding Hematol. disease

THE UCI APPROACH – Frequency  Twice weekly NST with weekly AFI  AFI twice weekly in postdates or AFI < 8.0  CST alternating w/ NST q3-4 days in DM  AFI is not as useful in DM, increased AFI  Twins with IUGR/discordance:  NST twice weekly, UAD + DVP weekly  Testing < 28 weeks: BPP primarily  NST is often not reassuring or equivocal due to neurologic immaturity

REASSURANCE?  Incidence of stillbirth within 1 week after a normal fetal assessment modality 3-5  1.9/1000 NSTs - NPR of 99.8%  0.3/1000 CSTs – NPR of 99.9%  0.8/1000 BPPs – NPR of 99.9%  0.8/1000 mBPPs – NPR of 99.9%  0/214 Dopplers in IUGR fetuses – NPR of 100% 6  They do not predict stillbirths related to acute changes in maternal-fetal status  Abruptio placentae  Umbilical cord accident  Achilles heel is high false positive rate (approx 35% CST, 55% NST)

Abnormal testing… now what?  Fix the offending disease process if possible i.e DKA, PNA  Perform a ‘back-up’ test (CST, BPP or prolonged monitoring), or repeat testing in short intervals 7  Ex. Decreased fetal movement + nonreactive NST  Term: CST [ deliver if positive or equivocal  Significantly preterm: BPP [ deliver, continuously monitor or retest in 24 hours, depending on results  If not reassured, hospitalize and weigh the risks and benefits of expediting delivery following consideration of gestational age and the disease state

THE UCI APPROACH: In general NST + AFI Nonreactive / AFI < 5 Both Normal Retest 3-4 days CST BPP Or 8 Positive < 6 Consider delivery CFM vs. daily NST Negative

IMPORTANT LINKS  PRACTICE BULLETIN Antepartum Fetal Surveillance PRACTICE BULLETIN Antepartum Fetal Surveillance

OTHER REFERENCES 1. Olesen AG. Acta Obstet Gynecol Scand Manning FA. AJOG Freeman RK. AJOG Miller DA. AJOG Manning FA. AJOG Almstrom H. Lancet Manning FA. AJOG