Maternal mortality in rural South Africa: the impact of case definition on levels and trends

Background: Uncertainty in the levels of global maternal mortality reflects data deficiencies, as well as differences in methods and definitions. This study presents levels and trends in maternal mortality in Agincourt, a rural subdistrict of South Africa, under long-term health and sociodemographic surveillance.

Methods: All deaths of women aged 15 years-49 years occurring in the study area between 1992 and 2010 were investigated, and causes of death were assessed by verbal autopsy. Two case definitions were used: "obstetrical" (direct) causes, defined as deaths caused by conditions listed under O00-O95 in International Classification of Diseases-10; and "pregnancy-related deaths", defined as any death occurring during the maternal risk period (pregnancy, delivery, 6 weeks postpartum), irrespective of cause.

Results: The case definition had a major impact on levels and trends in maternal mortality. The obstetric mortality ratio averaged 185 per 100,000 live births over the period (60 deaths), whereas the pregnancy-related mortality ratio averaged 423 per 100,000 live births (137 deaths). Results from both calculations increased over the period, with a peak around 2006, followed by a decline coincident with the national roll-out of Prevention of Mother-to-Child Transmission of HIV and antiretroviral treatment programs. Mortality increase from direct causes was mainly due to hypertension or sepsis. Mortality increase from other causes was primarily due to the rise in deaths from HIV/AIDS and pulmonary tuberculosis.

Conclusion: These trends underline the major fluctuations induced by emerging infectious diseases in South Africa, a country undergoing rapid and complex health transitions. Findings also pose questions about the most appropriate case definition for maternal mortality and emphasize the need for a consistent definition in order to better monitor and compare trends over time and across settings.