Abstract:
BACKGROUND : The assessment of fetal blood flow using Doppler waveform can be used to identify placental
insufficiency, and hence is a tool to identify fetuses at risk of stillbirth due to fetal growth restriction (FGR). In
South Africa the largest category of perinatal deaths is ‘unexplained intrauterine death’. The majority of the
mothers are clinically healthy women. This study was performed to determine the prevalence of abnormal
umbilical resistance indices (abnormal RI) to see if screening a low-risk pregnant population is worthwhile.
METHODS : A descriptive study across 9 sites in 8 provinces of South Africa was performed to determine the
prevalence of abnormal RI of the umbilical artery in women classified as having a low-risk pregnancy. The
study was conducted from 1st September 2017- February 2020.The pregnant women classified were
screened using a continuous wave Doppler ultrasound apparatus (UmbiflowTM) between 28 and 34 weeks’
gestation. Women with fetuses with an abnormal RI were referred to a high-risk clinic and were managed
according to standard protocol. The outcomes of all the deliveries were recorded.
FINDINGS : UmbiflowTM screening of the umbilical artery was performed in 7088 women across nine sites; 919
(13¢0%) fetuses had an abnormal RI. Absent end diastolic flow (AEDF) was found in 87 (1¢2%) fetuses. The
prevalence of small for gestational ages (SGA) babies was 23¢1% in the normal RI group and was significantly
higher in the abnormal RI group 32¢1% (p<0¢0001). There was a statistical difference in the perinatal mortality
rate between the normal RI (9.8/1000) and abnormal RI group (21.4/1000) [RR 0¢046; 95% CI -0¢06 0¢98].
INTERPRETATION : The prevalence of abnormal RI and AEDF in this screened low-risk population was about ten
times higher than that previously recorded in high income countries. Continuous wave Doppler ultrasound
screening detected previously undiagnosed growth restricted babies. The prevalence of AEDF warrants continuous
wave Doppler ultrasound screening of the low-risk pregnant population in South Africa.
