Determinants of Preterm Birth in Sub-Saharan Africa: A Systematic Review with Evidence from Nigeria

Preterm birth has ranked as one of the leading causes of neonatal mortality and morbidity in the world, with the most significant proportion of burden being based in Sub-Saharan Africa, with Nigeria bearing a disproportionate burden due to its population and the inability to overcome the health-system problem. In this study, observational evidence on determinants of preterm birth in Sub-Saharan Africa was systematically synthesised, with particular comparative evidence from Nigeria, using PRISMA-guided methods. Searches of major biomedical and African-based databases were conducted to identify studies published between 1990 and 2024 that examined associations between maternal sociodemographic, obstetric, clinical, and health-system factors and preterm birth (<37 weeks' gestation). These studies were synthesised through a narrative review and subjected to a structured comparative analysis. The prevalence of preterm birth was reported to be between 7.4 and 12.6 across the region, with hospital-based Nigerian cohorts at the top of this scale. Previous preterm birth (adjusted OR: 3.053) and multiple gestation (OR: 4.952) were the strongest predictors, indicating recurrent and biological effects. Maternal conditions, especially those involved with hypertensive (OR: 2.4–3.1) and anaemia (OR: 2.1–2.9), were strong and uniform across nations. Interestingly, health-system determinants were stronger in Nigeria, where the number of fewer than four antenatal care visits per woman nearly tripled the likelihood of preterm baby birth (OR: 2.53-3.6), which was higher in Nigeria than in the region. Poor maternal education and poverty as socioeconomic disadvantages predispose preterm birth by 30-90% in various environments. In general, preterm birth in Sub-Saharan Africa is an interaction of biological, social, and system-level factors, with Nigeria having more vulnerability due to modifiable health-governance failures and the necessity to create prevention-based maternal health policies.