OBJECTIVES: The COVID-19 pandemic affected provision and use of maternal health services. This study describes changes in obstetric complications, referrals, stillbirths and maternal deaths during the first year of the pandemic and elucidates pathways to these changes. DESIGN: Prospective observational mixed-methods study, combining monthly routine data (March 2019-February 2021) and qualitative data from prospective semi-structured interviews. Data were analysed separately, triangulated during synthesis and presented along three country-specific pandemic periods: first wave, slow period and second wave. SETTING: Six referral maternities in four sub-Saharan African countries: Guinea, Nigeria, Tanzania and Uganda. PARTICIPANTS: 22 skilled health personnel (SHP) working in the maternity wards of various cadres and seniority levels. RESULTS: Percentages of obstetric complications were constant in four of the six hospitals. The percentage of obstetric referrals received was stable in Guinea and increased at various times in other hospitals. SHP reported unpredictability in the number of referrals due to changing referral networks. All six hospitals registered a slight increase in stillbirths during the study period, the highest increase (by 30%-40%) was observed in Uganda. Four hospitals registered increases in facility maternal mortality ratio; the highest increase was in Guinea (by 158%), which had a relatively mild COVID-19 epidemic. These increases were not due to mortality among women with COVID-19. The main pathways leading to these trends were delayed care utilisation and disruptions in accessing care, including sub-optimal referral linkages and health service closures. CONCLUSIONS: Maternal and perinatal survival was negatively affected in referral hospitals in sub-Saharan Africa during COVID-19. Routine data systems in referral hospitals must be fully used as they hold potential in informing adaptations of maternal care services. If combined with information on women's and care providers' needs, this can contribute to ensuring continuation of essential care provision during emergency.