Prediction of perinatal morbidity at term in small fetuses: comparison of fetal growth and Doppler ultrasound

Abstract

Objective: To compare fetal growth assessed by ultrasound (change in standard deviation score of abdominal circumference and estimated fetal weight) during the third trimester with predelivery ultrasound measurements of fetal size and Doppler measurements from the umbilical and fetal arteries in order to predict suboptimal perinatal outcome in small babies at term.

Design: Prospective observational study.

Setting: Day assessment unit in a university hospital.

Subjects: One hundred and four consecutive women with a clinical suspicion of a small fetus during the third trimester confirmed by ultrasound (abdominal circumference below the 10th centile) and ultimately delivered at term.

Main outcome measures: Acidaemia at birth, fetal distress requiring emergency caesarean section in labour, admission to the neonatal intensive care unit.

Results: Ninety-four babies (90%) weighed less than the 10th centile and the incidence of suboptimal perinatal outcome was 27%. The largest areas under the receiver operating characteristic curves for suboptimal perinatal outcome were obtained with the change in standard deviation score of abdominal circumference and estimated fetal weight, and the ratios of aortic/middle cerebral and renal/middle cerebral pulsatility index. Although low, the odds ratios of the change in estimated fetal weight standard deviation score and the Doppler ratios were significantly different from zero.

Conclusion: Ultrasound assessment of fetal growth and predelivery fetal Doppler pulsatility index ratios were superior to predelivery estimates of fetal size and umbilical artery pulsatility index in predicting suboptimal perinatal outcome in small fetuses delivering at term, although the clinical value of such a prediction may be limited.