Screening and managing a low-risk pregnant population using continuous-wave Doppler ultrasound in a low-income population: A cohort analytical study

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.

INTERGROWTH-21st v. local South African growth standards (Theron-Thompson) for identification of small-for-gestational-age fetuses in stillbirths: A closer look at variation across pregnancy

“…[20] In addition, it must be acknowledged that growth restriction may also occur in AGA pregnancies. [21] This was observed in our study, where one-fifth of stillbirths with IUGR as the primary cause of death were AGA (using either growth chart). Umbilical artery Doppler measurements using an inexpensive hand-held device such as the Umbiflow can be used to identify such cases.…”

Portable Continuous Wave Doppler Ultrasound for Primary Healthcare in South Africa: Can the EUnetHTA Core Model Guide Evaluation Before Technology Adoption?

“…It was initially aimed at reducing unnecessary referrals for pregnant women with fetuses, which were SGA [33]. Findings showed that this continuouswave DUS was effective in screening low-risk pregnancies, identifying at-risk fetuses requiring interventions, and in reduction of additional tests arising from false negative results [28].…”

“…Timely detection of abnormalities in the blood ow in the uterine artery followed by management of undiagnosed placental insu ciency could lead to prevention of perinatal deaths [6,28,34]. Appropriate management will depend on the severity and the gestation of the pregnancy.…”

“…Currently, no effective antenatal therapy exists for fetal growth restriction; hence, delivery could be the only viable option [35]. A recent study observed a 1.5% prevalence of absent end diastolic ow (AEDF), a sign of fetal vascular stress, in a population of low-risk pregnancies, indicating that using the Doppler RI information in the study population reduced the rate of macerated stillbirth by 60% [28,34].…”

“…Legend: Patient pathway on introduction of Umbi owTM into the clinical system in South Afri-ca. Adopted from Nkosi et al 2019 [28].…”