Maternal and neonatal outcomes in The Gambia, 2022–2024: prospective pregnancy surveillance to strengthen maternal immunization safety monitoring

BACKGROUND: Reliable background estimates of adverse maternal and neonatal outcomes are needed to interpret safety signals as maternal vaccines are introduced but remain limited in many African settings. We established facility-based pregnancy registries in The Gambia to estimate site-specific background rates of selected adverse events of special interest (AESIs) relevant to maternal immunization safety monitoring. METHODS: We conducted prospective observational surveillance from August 2022 to August 2024 at three high-volume antenatal care facilities in the Western Region of The Gambia. Pregnant women aged 18 years or older were enrolled during routine antenatal care and followed through delivery to the 4-6-week postnatal visit. Selected AESIs were ascertained irrespective of vaccination status and delivery location, using routinely available clinical records. Diagnostic certainty was assessed using Global Alignment of Immunization Safety Assessment in Pregnancy (GAIA) definitions. Outcome-specific rates were calculated with 95% confidence intervals (CIs). RESULTS: Among 5099 enrolled women, 419 (8%) discontinued participation or were lost to follow-up. We recorded 4680 deliveries resulting in 4775 infants, including 4671 live births and 104 stillbirths. Six maternal deaths were recorded, corresponding to a maternal mortality rate of 1.3 per 1000 births (95% CI: 0.5-2.7). Stillbirth and neonatal mortality rates were 21.8 (17.8-26.3) and 15.6 (12.3-19.6) per 1000 live births, respectively. There were 398 preterm births, 277 infants with low birth weight and two babies with major external structural congenital anomalies. CONCLUSIONS: Surveillance embedded in routine antenatal care generated site-specific background rates of selected adverse maternal and neonatal outcomes relevant to maternal immunization safety monitoring. Strengthening clinical documentation, diagnostic capacity, and vaccination history ascertainment could improve outcome classification and the utility of these platforms for future safety monitoring.