Maternal serum vitamin D levels and preeclampsia among Kenyan pregnant women: A matched case-control study

Abstract

Background Preeclampsia accounts for about one in five direct maternal deaths in Kenya. Low vitamin D levels have been linked to its pathophysiology. Despite this, context‑specific data from African populations remain limited. The study aimed to determine the association between maternal serum 25-hydroxyvitamin D [25(OH)D] concentrations (nmol/L) in pregnancy and the risk of preeclampsia in a Kenyan population. Methods A matched case-control study was conducted at Moi Teaching and Referral Hospital, Kenya. A total of 118 women with confirmed viable intrauterine pregnancies at ≥28 weeks’ gestation were analysed. Fifty-nine women with preeclampsia (cases) and 59 controls were matched by parity, gestation, and age. Serum 25(OH)D was quantified. Vitamin D status was categorised as suboptimal (<50 nmol/L) or sufficient (≥50 nmol/L) status. The association between vitamin D status and preeclampsia was assessed using conditional logistic regression. Odds ratios (ORs) with 95% confidence intervals (CIs) were presented. Results Median serum 25(OH)D was significantly lower in preeclampsia cases compared with controls [67.1 nmol/L (interquartile range 47.8–84.0) vs. 77.6 nmol/L (62.4–99.7); P = 0.001]. Suboptimal vitamin D levels (<50 nmol/L) were observed in 32.2% of preeclampsia cases versus 6.8% of controls (P = 0.002). In conditional logistic regression accounting for matching, women with suboptimal vitamin D had higher odds of preeclampsia (OR 8.0; 95% CI: 1.84–34.78; P = 0.006). Each 10 nmol/L decrease in serum 25(OH)D was associated with a 29% increase in preeclampsia odds (OR 1.29; 95% CI: 1.09–1.54; P = 0.004). Conclusions In this study, suboptimal maternal serum vitamin D status demonstrated a significant association with preeclampsia. There is potential value in antenatal screening for vitamin D status. Findings support further research into vitamin D supplementation as a preventive intervention for preeclampsia. Trial registration Pan African Clinical Trial Registry (PACTR202505516303679).