Interpretation
Reinebrant and colleagues’ seminal work14 provided a comprehensive overview of the causes of stillbirth around the globe. In our review, we built upon this foundation by investigating ethnic variation of causes of stillbirth in high-income countries. While perinatal outcomes in some ethnic minority groups appear to have improved over time, disparities in stillbirth rates based on ethnicity continue to persist in the majority of reported cases.7-9, 34, 36, 39, 40, 49-59 Ethnicities with the largest sample sizes (Caucasian, African and Hispanic) overall showed similar proportions in the causes of stillbirth. Compared to non-Indigenous Australians, Indigenous Australian women showed higher frequencies of stillbirth attributed to other complications of labour and delivery. This category includes stillbirth that has been attributed to malpresentation, forceps delivery, vacuum delivery, caesarean delivery or induction of labour. This is in agreement with a population-based study from the Northern Territory, Australia which demonstrated higher rates of emergency caesarean and malpresentation in Indigenous mothers compared to non-Indigenous,60 but contrary to the study by Kildea and colleagues who found Indigenous Australian to have lower rates of instrumental delivery and induction of labour.61 In our review, Asian and South Asian ethnicities showed a larger proportion of stillbirths attributed to complications of placenta, cord and membranes, in line with previous work showing higher rates of placental insufficiency62and placenta praevia63 in women of Asian heritage. However, the utility of the interpretation of differences observed in Indigenous Australian, Asian and South Asian women is limited due to their small sample sizes.
Our findings imply that the higher incidence of stillbirths observed in minority ethnic groups in previous studies are likely to be a consequence of factors other than intrinsic differences such as culturally inappropriate antenatal care64 and higher incidence of modifiable risk factors such as obesity, maternal smoking, hypertension, and diabetes.12 The effect of the migration experience and the associated socioeconomic disadvantage migrants may face is difficult to dissect from intrinsic differences between various ethnic groups, if any, with regards to stillbirth outcomes.24, 65-67 Gibson-Helm and colleagues68 found that after adjusting for confounding factors such as age, parity, BMI and relative socio-economic disadvantage, the difference in stillbirth rates between migrants and women from host countries disappeared. These results, together with findings from our study, suggest that socio-cultural-economic factors may be more important in explaining the disparities in stillbirth rates between ethnic groups rather than intrinsic differences.