Maternal-Fetal Medicine
Maternal-fetal medicine tests complicated pregnancy: hypertensive disease, fetal growth, preterm birth, multiple gestation, and medical disorders in pregnancy. Questions often ask when to deliver and which surveillance test to use.
Core rules
- Fetal growth restriction is an estimated fetal weight or abdominal circumference below the 10th centile with Doppler abnormality or growth faltering; umbilical artery Doppler guides timing. Absent or reversed end-diastolic flow is a sign of severe placental insufficiency.
- Preeclampsia with severe features includes BP ≥160/110, platelets <100,000, transaminases more than twice normal, creatinine >1.1 mg/dL, pulmonary edema, or cerebral/visual symptoms. Deliver at ≥34 weeks; give magnesium sulfate for seizure prophylaxis.
- Preterm labor before 37 weeks: give antenatal corticosteroids at 24-34 weeks; give magnesium sulfate for fetal neuroprotection before 32 weeks; use tocolysis for 48 hours to allow steroids to act.
- PPROM: avoid digital cervical examination; perform a speculum examination, give latency antibiotics, and monitor for chorioamnionitis.
- Determine chorionicity in multiple pregnancy by first-trimester ultrasound; monochorionic twins need surveillance for twin-twin transfusion syndrome.
Worked example
A 31-year-old at 33 weeks has BP 165/110, platelets 90,000, and headache. Reasoning: this is severe preeclampsia. Give IV labetalol or hydralazine, magnesium sulfate, and betamethasone, then plan delivery after steroids. At 33 weeks, severe features outweigh the risks of prematurity, so delivery is indicated.
Traps
- Diagnosing fetal growth restriction from a single abdominal circumference without Doppler or interval growth.
- Delaying delivery in severe preeclampsia at or beyond 34 weeks.
- Performing a digital cervical examination in PPROM.