RESUMEN
Nigeria has a plural legal system in which various sources of law govern simultaneously. Inconsistent and conflicting legal frameworks can reinforce pre-existing health disparities in sexual and reproductive health (SRH). While previous studies indicate poor SRH outcomes for Nigerian women and girls, particularly in Northern states, the relationship between customary and religious law (CRL) and SRH has not been explored. We conducted a state-level ecological study to examine the relationship between CRL and SRH outcomes among women in 36 Nigerian states and the Federal Capital Territory of Abuja (n = 37), using publicly available Demographic and Health Survey data from 2013. Indicators were guided by published research and included contraception use among married women, total fertility rate, median age at first birth, receipt of antenatal care, delivery location, and comprehensive knowledge of HIV. To account for economic differences between states, crude linear regression models were compared to a multivariable model, adjusting for per capita GDP. All SRH outcomes, except comprehensive knowledge of HIV, were statistically significantly more negative in CRL states compared to non-CRL states, even after accounting for state-level GDP. In CRL states in 2013, compared to non-CRL states, the proportion of married women who used any method of contraception was 22.7 percentage points lower ([95% CI: -15.78 --29.64], p<0.001), a difference that persisted in a model adjusting for per capita GDP (b[adj] = -16.15, 95% CI: [-8.64 --23.66], p<0.001.). While this analysis of retrospective state-level data found robust associations between CRL and poor SRH outcomes, future research should incorporate prospective individual-level data to further elucidate these findings.