Introduction Maternal mortality in sub-Saharan Africa remains high, with the rate of decline stagnated. Many countries conduct maternal reviews, which can help identify outliers. Outlier analysis could better inform the design and implementation of strategies to tackle the causes of preventable maternal deaths. Aim To examine the variability in causes of maternal deaths in African countries using the WHO International Classification of Diseases Maternal Mortality (ICD-MM) framework and the contributing factors using the three-delays framework. Methods An observational ecological study of national maternal death review reports from 23 African countries between 2009 and 2022. Results Twenty-three maternal death review reports, covering 19,319 deaths, were included. Direct causes were the most common (43-92%), with variability across ICD-MM groups and three-delay factors observed. Obstetric haemorrhage (ICD-MM Group 3) was the leading cause in 17 reports, non-obstetric complications (Group 7) in five, pregnancy with abortive outcomes (Group 1) in one, and hypertensive disorders (Group 2) in one, with varying magnitudes across countries. Most reports (94%) identified the third delay (delay in receiving adequate care) as the primary contributor, while one report cited the first delay (delay in decision to seek care). The magnitude of each delay varied by country: The first delay contributed 0-34% of the audited maternal deaths; the second delay, 5-44%; and the third delay, 32-100%. Conclusion Efforts to further reduce the burden of preventable maternal deaths in sub-Saharan Africa should prioritise addressing the third delay, i.e. the delay in receiving adequate care within health facilities.