Prediction of morbidity in small and normally grown fetuses by fetal heart rate variability, biophysical profile score and umbilical artery Doppler studies

Abstract

Objective: To assess the ability of noninvasive tests of fetal wellbeing to predict hypoxic morbidity independent of fetal size.

Design: A prospectively planned, longitudinal, observational study.

Setting: Fetal Surveillance Unit, King's College Hospital, London.

Subjects: One hundred and ninety-one pregnant women with singleton pregnancies who were delivered after 32 weeks' gestation who were seen in the Fetal Surveillance Unit within seven days of delivery.

Interventions: Fetal surveillance by fetal abdominal circumference, heart rate variability (mean range), biophysical profile score and umbilical artery pulsatility index measurements.

Main outcome measures: Birthweight was classified as > or < or = 2.5th centile (AGA or SGA) for gestational age and sex. Morbidity was defined as at least one of the following at birth: delivery by emergency caesarean section for fetal distress, umbilical venous blood pH less than 7.15, 5 min Apgar score less than 7 or admission to the Special Care Baby Unit (SCBU).

Results: Fetal abdominal circumference was the best indicator of which fetuses (n = 30) would be SGA. Fourteen of the 30 (47%) SGA fetuses had morbidity at birth and abnormal umbilical Doppler studies significantly predicted this (chi 2 = 2.93, P = 0.003). By contrast, fetal heart rate variability and the biophysical profile score did not. Twenty-seven of the 161 (17%) AGA fetuses had morbidity at birth, but this was not significantly predicted by heart rate variability, biophysical profile score or umbilical Doppler studies.

Conclusions: None of the antenatal testing techniques studied predicted morbidity in normally grown fetuses but Doppler studies indicated whether a small fetus was 'sick small' or 'normal small'.