Abstract:
BACKGROUND: In South Africa (SA), the largest category of perinatal deaths is unexplained stillbirths. Two-thirds of these occur in the
antenatal period and most fetuses are macerated, but at antenatal clinics the mothers were generally regarded as healthy, with low-risk
pregnancies. Innovative methods are urgently required to detect fetuses at risk of stillbirth and manage the mothers appropriately.
OBJECTIVES: To determine the prevalence of raised resistance indices (RIs) of the umbilical artery in a low-risk, low-income population and
ascertain whether use of this information can prevent perinatal deaths.
METHODS: A descriptive study was performed in Mamelodi township, east of Pretoria, SA, on pregnant women attending antenatal clinics
draining to two community health centres (CHCs). These women, classified as having low-risk pregnancies, were screened for placental
insufficiency using a continuous-wave Doppler ultrasound apparatus (Umbiflow) between 28 and 32 weeks’ gestation. When a raised RI was
detected, the mother was referred to a high-risk clinic and managed according to a standard protocol. A cohort analytical study compared
women who attended antenatal care at the same clinics as the Umbiflow group but did not have an Umbiflow test with those who had an
Umbiflow test. The outcomes of all the deliveries in Mamelodi were recorded. The prevalences of abnormal RIs, absent end-diastolic flow
(AEDF), stillbirths and neonatal deaths were the main outcome measures.
RESULTS: An Umbiflow RI was performed in 2 868 women, and pregnancy outcome was available for 2 539 fetuses (88.5%); 297 fetuses
(11.7%) were regarded as at high risk. AEDF was found in 1.5% of the population screened with an outcome. There were 29 perinatal
deaths in the Umbiflow group (low risk n=18, high risk n=11). The perinatal mortality rate for 12 168 women attending the CHCs and the
antenatal clinics draining to the CHCs who did not have an RI was 21.3/1 000 births, significantly higher than that in the Umbiflow group
(11.4/1 000 births) (risk ratio 0.58, 95% confidence interval 0.42 - 0.81).
CONCLUSIONS: The prevalence of AEDF in this low-risk population is ~10 times higher than that previously recorded. Use of the information
prevented a number of perinatal deaths, most of which would have been macerated stillbirths. Screening a low-risk pregnant population
using continuous-wave Doppler ultrasound may substantially reduce the prevalence of unexplained stillbirths in SA.
