RESUMEN
PURPOSE: Myelomeningocele is the most severe birth defect compatible with long-term survival. It accounts for 5.7% of neurological surgeries in Nigeria. However, the exact cause of this neural tube defect remains unidentified. This study aims to determine if seasonal variation is a potential environmental contributor. METHOD: This study prospectively recruited 242 children diagnosed with myelomeningocele at the University of Nigeria Teaching Hospital (UNTH), Enugu, Nigeria, between January 2010 and December 2022. Our primary outcome was the seasonal occurrence of myelomeningocele, while covariates included gender, birth order, maternal folic acid supplementation (FAS), and parental age. The estimated month of conception was derived from the mother's last menstrual period (LMP), and the occurrence of myelomeningocele across the various seasons in which these babies were conceived was assessed using the Lorenz curve and the Gini coefficient. RESULTS: 242 patients were studied with a male-to-female ratio of 1.26. The majority of cases were lumbosacral (93.4%), and none of the mothers commenced FAS before conception. The highest proportion of cases (39.7%) occurred during the hottest period of the dry season (January-March), while the lowest proportion (15.7%) occurred during the early wet season (April-June). The Gini index of 0.29, and the Gini coefficient derived from 100,000 Monte Carlo simulations of 0.24, indicate a significant variation in the distribution of myelomeningocele cases across different seasons of conception. CONCLUSION: The seasonal occurrence of myelomeningocele with a peak in January-March suggests a potential association with environmental factors including oxidative stress induced by solar radiation.