Introduction
Placental insufficiency means the placenta cannot supply enough oxygen and nutrients. Its main clinical expression is fetal growth restriction (FGR); at worst it ends in fetal hypoxia and stillbirth.
Definitions
- Small for gestational age (SGA): estimated weight or abdominal circumference below the 10th centile; many are constitutionally small and healthy.
- Fetal growth restriction: a fetus that has not reached its growth potential; suggested by weight < 3rd centile, or < 10th centile with abnormal Doppler, or growth falling across centiles.
- Early-onset (< 32 weeks) is usually severe placental disease with abnormal umbilical Doppler; late-onset (≥ 32 weeks) is milder but common and often missed.
Diagnosis
- Fundal height lagging by > 2 cm, or low weight gain, prompts an ultrasound.
- Serial biometry (estimated fetal weight, abdominal circumference) at least 2 weeks apart.
- Amniotic fluid: oligohydramnios (less renal perfusion).
- Doppler: raised resistance in the umbilical artery, then absent or reversed end-diastolic flow; low resistance in the middle cerebral artery (brain-sparing); abnormal ductus venosus flow is a late sign of decompensation.
- CTG: reduced variability, late decelerations.
- Look for a cause: anomaly scan, infection serology, karyotype if early and severe; check the mother's BP and urine.