Seasonal and Climatic Variation in Hospital Presentations of Hypertensive Disorders of Pregnancy at a Sahelian Nigerian Tertiary Hospital: A Five-Year Time-Series and Correlation Analysis

Hypertensive disorders of pregnancy (HDP) remain a major cause of maternal mortality in Nigeria, but evidence on whether HDP varies with local climatic conditions in the Sudano-Sahelian zone of West Africa, which has a single rainy season, is limited. This retrospective ecological time-series study analysed 907 HDP case records (chronic hypertension, gestational hypertension, preeclampsia, superimposed preeclampsia and eclampsia) managed at Usmanu Danfodiyo University Teaching Hospital (UDUTH), Sokoto, Nigeria, over 60 months (January 2020–December 2024). Monthly case counts were linked to monthly hospital deliveries (n = 15,730) and to climatic data from the Nigerian Meteorological Agency (NiMet). Outcomes were the monthly HDP case count and hospital-based prevalence (HDP cases per 100 deliveries). Trends were assessed with linear regression and the Mann-Kendall test. Seasonal variation (two-season and five-season classifications) was assessed with negative binomial regression using a delivery offset, harmonic seasonal terms and autocorrelation-consistent standard errors; Pearson and Spearman correlations related monthly outcomes to climatic indicators. HDP presentations were stable over time (Mann-Kendall p = 0.81). Monthly totals ranged from a December low (49 cases) to an August peak (112 cases). After adjustment for season length and delivery volume, prevalence was highest in the peak rainy (7.43 per 100 deliveries) and early rainy (7.10) seasons and lowest in the post-rainy season (4.56); the hot-dry season’s larger raw share of cases (24.8%) reflected its three-month duration. Prevalence was higher in the rainy than the dry season (7.26 vs. 5.22 per 100 deliveries; incidence rate ratio [IRR] 1.42, 95% CI 1.09–1.84).