A stillbirth is defined as a fetus being born with no signs of life at or after 28 weeks of pregnancy. Stillbirths are a global problem with approximately 2.6 million deaths being recorded in 2016, with the largest proportion of stillbirths occurring in low and middle-income countries.
In South Africa, the largest category of perinatal deaths is "unexplained stillbirths" that amounted to around 12 000 cases in 2016. Stillbirths can be caused by several factors such as placental dysfunction (leading to growth restriction), infections, and birth defects. A number of these risk factors can be detected during pregnancy and therefore aid health care providers in decreasing the incidence of stillbirths.
The use of Doppler ultrasound in the assessment of blood flow in fetal umbilical vessels has long been recognized. Abnormal fetal flow in the umbilical artery correlates strongly with intrauterine growth restriction, with absent or reversed end-diastolic flow carrying a high risk of fetal and neonatal outcome. The investigation of umbilical vessels using Doppler ultrasound may assist in the early detection and quantification of placental insufficiency in fetuses.
The former "continuous-wave" (CW) Doppler ultrasound was replaced with "pulsed-wave" (PW) Doppler incorporated in ultrasound machines, which is mostly only available in high resource settings and requires a high level of technical skills. Presently, the only way to determine the fetal growth at primary care level in South Africa is by measuring the Symphysis fundal (SF) height, which measures the size of the uterus, plotted against gestational age and is used to assess fetal growth during pregnancy. However, this measurement is not always reliable: poor SF growth could be a result of a fetus with problems (fetal growth restriction) or a normal small baby (small for gestational age). An accurate low-cost method for detecting abnormal growth is desirable, especially in low and middle-income countries where ultrasound is not widely available.
The South African Medical Research Council (SAMRC) and Council for Scientific Research (CSIR) funded the development of the Umbiflow device in collaboration with the Gauteng, Western Cape, and National Department of Health. Umbiflow is a low-cost, handheld, mobile CW Doppler ultrasound device that has shown to have the potential to reduce the perinatal mortality by up to 40% in a low-income setting. The device does not require specialist skills to operate, interpretation of results is simple and it can be used by nurses, midwives and general practitioners in rural and low-resource primary health care settings.
The device uses CW Doppler ultrasound to measure blood flow in the fetal umbilical artery and can be used to detect and quantify placental insufficiency in pregnant women. When abnormal flow or resistance indices (RI) are detected, a woman can be referred to a higher level of care to prevent adverse fetal or neonatal outcomes.
A cohort analytical study conducted in Mamelodi, a low-income community in the east of Pretoria, set out to investigate the prevalence of abnormal flow in the umbilical artery using the Umbiflow device. Women considered to be high risk (11,7% in Umbiflow group) with a RI above the 75th percentile for the gestational age were referred to a high-risk clinic where a detailed ultrasound examination was carried out and the necessary precautions were implemented. The active management of the newly identified high-risk pregnancies improved perinatal outcome significantly. Absent end-diastolic flow (AEDF) was found in 1.5% of the Umbiflow group, a 5-10 times higher prevalence of AEDF than recorded in other studies screening low-risk or unselected populations.
The study is currently the first large scale study using continuous wave Doppler ultrasound to screen a pregnant population classified as low risk in a low-income setting. The study reported an overall lower perinatal mortality rate in the Umbiflow group (11.4/1000 births) compared to the control group (21.3/1000 births), the greatest reduction being in macerated stillbirths.
The device presents an opportunity to effectively screen all women for abnormal Doppler flow velocities to reduce unexpected fetal death. The findings of this study were published in the South African Medical Journal, “Screening and managing a low-risk pregnant population using continuous-wave Doppler ultrasound in a low-income population: A cohort analytical study.”