Late-Onset Fetal Growth Restriction

Late onset fetal growth restriction is growth restriction diagnosed at 32 weeks or later, defined by an abdominal circumference or estimated weight below the 3rd centile, or below the 10th centile with a low cerebroplacental ratio or raised uterine artery resistance. The umbilical artery Doppler is often normal, so it is easily missed. It is the commonest form of growth restriction and matters because it causes stillbirth and hypoxia in labour.

• Risk factors: chronic hypertension, smoking, previous small baby, anaemia, malaria, low weight gain, age above 35 years.
• Often found after reduced fetal movements.
• Induction at 37 weeks lowers stillbirth.

Women have a small fundal height or reduced fetal movements, and some have hypertension. Most are asymptomatic.

• Fundal height below the 10th centile.
• Normal or mildly low liquor.
• Differential diagnosis: constitutionally small fetus, wrong dates, early onset growth restriction, fetal infection, fetal anomaly, oligohydramnios.
• Complications: stillbirth, intrapartum fetal distress, emergency caesarean birth, neonatal hypoglycaemia, neonatal acidosis, neonatal death.

The approach is ultrasound with cerebroplacental assessment.

• Ultrasound: abdominal circumference or estimated fetal weight below the 3rd centile, or crossing 2 quartiles of growth, or size below the 10th centile with abnormal Doppler.
• Cerebroplacental ratio below the 5th centile (or below 1.08), middle cerebral artery pulsatility index below the 5th centile, umbilical artery pulsatility index above the 95th centile, uterine artery pulsatility index above the 95th centile.
• Liquor volume (deepest pocket below 2 cm); cardiotocography.
• Maternal tests: blood pressure, urine protein, full blood count, malaria rapid test, glucose, syphilis and HIV tests.

The principle is surveillance with Doppler and cardiotocography and induction at 37 weeks when growth is restricted.

• Supportive: daily fetal movement counts; left lateral rest; stop smoking; treat anaemia and infection; deliver in a facility with continuous cardiotocography and caesarean ability.
• Pharmacological: labetalol 200 mg oral every 8 to 12 hours (maximum 2.4 g daily) or nifedipine modified release 30 to 60 mg oral once daily (maximum 120 mg) for blood pressure 140/90 mmHg or more; artemether-lumefantrine 4 tablets (each 20 mg and 120 mg) oral at 0, 8, 24, 36, 48 and 60 hours for malaria; ferrous sulphate 200 mg oral 8-hourly for anaemia; betamethasone 12 mg IM twice, 24 hours apart, only when delivery is planned before 35 weeks; oxytocin 10 IU IM at birth.
• Procedures: induction at 37 weeks for an estimated weight below the 3rd centile or a cerebroplacental ratio below the 5th centile, and at 38 weeks when only one test is abnormal; induction with misoprostol 25 micrograms vaginal 6-hourly (maximum 4 doses) or Foley catheter with a 30 mL balloon, with continuous cardiotocography; earlier delivery for abnormal umbilical artery Doppler, reduced movements or pathological cardiotocography.
• Special groups: newborns feed within 30 minutes, have glucose checked at 2 hours, and glucose below 2.6 mmol/L is treated with dextrose 10 percent 2 mL/kg IV over 10 minutes then 80 mL/kg per day.
• Red flags: reduced fetal movements, abnormal umbilical artery flow, oligohydramnios, abnormal cardiotocography, hypertension, bleeding.
• Follow-up: Doppler and growth every 1 to 2 weeks; cardiotocography twice weekly; newborn weight and glucose monitoring.