Doppler ultrasound to improve prediction of adverse perinatal outcomes in low resource settings
Authors:   , Ali Sam 
Published: December 2022

Chapter 1 provides the general background for the thesis, providing an overview of the global burden and trends of stillbirths. While most stillbirths result from preventable causes, the possible reasons behind the lack of their substantial drop remain unclear. We highlight the potential of Doppler ultrasound to improve perinatal outcomes.

In Chapter 2, we reviewed available literature on the prognostic accuracy of Doppler ultrasound for adverse perinatal outcomes in LMICs. We identified 2825 records, and 30 studies (including 4977 women) from Africa (40.0%, n=12), Asia (56.7%, n=17) and South America (3.3%, n=01) were included. Most studies were of suboptimal quality. Evidence to guide how Doppler ultrasound should be used in LMICs was lacking. We recommend well- designed primary studies, and standardisation of practice and definitions of adverse perinatal outcomes across settings as per the International Classification of Diseases-10 Perinatal Mortality.

In Chapter 3, we aimed to determine the quality of fetal biometry and pulse- wave Doppler ultrasound measurements in our study. The quality scores of our ultrasound measurements were high, with over 84.8% of the pulse-wave Doppler images and 88.0% of the biometry images scored as acceptable. The inter-rater agreement was very good for Doppler and biometry images, with adjusted Kappa coefficient of up to 0.94 (95% CI, 0.87–0.99) for the umbilical artery and 0.94 (95% CI, 0.87–0.98) for the HC measurements. Training local healthcare providers to perform Doppler ultrasound and implementing of quality control systems in our clinical and research settings was feasible.

In Chapter 4, we explored the views of women and healthcare providers regarding the use of advanced ultrasound technology in pregnancy. We found that spousal involvement may promote acceptance and use of ultrasound services. However, the health workers did not have adequate knowledge about Doppler technology and using it for the benefit of mothers and the mothers feared that ultrasound procedures might harm them or their unborn babies.

Chapter 5 evaluates the prevalence of abnormal Doppler ultrasound and the association with adverse perinatal outcomes. Low cerebroplacental ratio (CPR) was strongly associated with stillbirth (OR 4.82, 95% CI 1.09–21.30). CPR and middle cerebral artery (MCA) PI below the fifth percentile were independently associated with a composite perinatal outcome (defined as the occurrence of one or more of the following: stillbirths (intrauterine fetal death after 28 weeks of gestation, neonatal death within 28 days of the postnatal period, admission to neonatal intensive care unit (NICU) for >24 hours, Apgar score of <7 at 5 minutes, emergency caesarean birth for fetal distress (based on abnormal fetal heart rate monitoring) and respiratory distress syndrome (RDS)); the association with MCA PI was stronger in small- for-gestational-age neonates (OR 3.75, 95% CI 1.18–11.88). Fetuses with abnormal MCA PI or CPR near-term were at increased risk of stillbirth and perinatal complications.

In Chapter 6 we develop and internally validate a multivariable prediction model to estimate the risk of perinatal death and stillbirth in women near- term in Uganda. In a model combining maternal characteristics with MCA PI or CPR, the AUCs for predicting perinatal death were 0.78 (95% CI: 0.67–0.87) and 0.78 (95% CI: 0.65–0.87), respectively, in the development set. The bootstrap corrected AUC was 0.71, with a slope of 0.70. The predictive performance of our model was only moderate and below clinically relevant threshold. Its performance could be enhanced by addition of other important clinical tests like biomarkers and maternal cardiac function indicators.

Chapter 7 comprehensively discusses, based on what we have learnt from the current study and beyond, the potential for Doppler ultrasound to improve the quality of ANC and perinatal health in settings with high burden of stillbirths.