A randomized trial using ultrasound to identify the high-risk fetus in a low-risk population

To evaluate the effect of introducing two biophysical ultrasound examinations in a low-risk antenatal population. Scans were performed at 30-32 weeks' gestation and 36-37 weeks' gestation.

Scans assessed placental maturity, amniotic fluid volume, and estimated fetal weight. One thousand nine hundred ninety-eight low-risk patients were randomized at 30 weeks' gestation to a control group receiving standard antenatal care, or to the study group who also received an ultrasound scan. Outcome measures were frequency of small for dates (less than 10th percentile at birth), intervention rates, and admissions to neonatal intensive care.

The proportion of infants assessed as small for dates at birth in the study group was 6.9% (69 of 994) compared with 10.4% (104 of 999) in the control group (P =.008). The rates of intervention in the study and control groups were 31.3% (313 of 999) and 16.9% (169 of 999), respectively (P <.001). Twenty-eight (2.8%) neonates in the study group were admitted to the neonatal unit compared with 34 (3.4%) in the control group (P =.532).

Introduction of an ultrasound scan at 30-32 weeks' and 36-37 weeks' gestation may reduce the risk of a growth-restricted infant and increases antenatal interventions. Rates of admission to a neonatal unit are not significantly affected.