Temporal trends and maternal factors associated with congenital anomalies among live births in São Paulo, Brazil: a population-based study, 2015–2023

BACKGROUND: Congenital anomalies are a major cause of infant morbidity, mortality, and long-term disability worldwide. Their occurrence is influenced by maternal, demographic, and healthcare-related factors, and temporal patterns may vary according to anomaly group and surveillance quality. In Brazil, population-based analyses remain limited, especially those examining overall prevalence together with system-specific trends. METHODS: This population-based retrospective study used data from the Brazilian Live Birth Information System (SINASC). All live births registered in São Paulo between 2015 and 2023 were eligible. Annual prevalence rates of congenital anomalies were calculated per 10,000 live births with 95% confidence intervals (95% CI). Maternal, pregnancy, and neonatal characteristics were compared according to congenital anomaly status using Pearson's chi-square test. Temporal comparisons across predefined epidemiological periods were performed using count regression models with live births as the offset. Annual temporal trends were further assessed using log-linear and segmented trend models, with annual percent changes (APC) estimated for overall prevalence and major anomaly groups. Factors associated with congenital anomalies were assessed using adjusted logistic regression. RESULTS: A total of 4,329,485 live births were analyzed, of which 53,217 (1.23%) presented congenital anomalies. Overall prevalence increased from 103.90 per 10,000 live births in 2015 to 143.92 in 2023. In segmented trend analysis, total congenital anomaly prevalence increased by 2.01% per year (95% CI 0.17-3.89). Musculoskeletal anomalies were the most frequent group throughout the series, whereas circulatory anomalies showed a sustained increase (APC = 5.78%; 95% CI 3.46-8.15). Digestive anomalies showed a marked recent increase after 2022, while nervous system anomalies declined from 2017 onward (APC = - 5.25%; 95% CI - 9.30 to - 1.03). In exploratory period-based analyses, 2023 had a higher rate than the 2018-2019 baseline in the negative binomial model (IRR = 1.179; 95% CI 1.028-1.353; p = 0.0188), while no significant differences were found for the Zika or COVID-19 periods. In the adjusted model, higher odds of congenital anomalies were observed among male newborns, older mothers, and multiple pregnancies, whereas prenatal care was associated with lower recorded odds. CONCLUSIONS: Congenital anomaly prevalence increased in São Paulo between 2015 and 2023, accompanied mainly by increases in circulatory and digestive system anomalies. These findings highlight the importance of continuous population-based surveillance and system-specific trend analysis.