Background: Magnesium plays a critical role in metabolism especially with respect to carbohydrate, protein and energy syntheses, and it is known to decline in pregnancy. A suggested role for magnesium deficiency in the genesis of preeclampsia, gestational diabetes, intrauterine growth restriction, muscle cramps and preterm delivery has prompted studies with conflicting evidence. Assessing the prevailing serum magnesium levels in our locale and identifying maternal characteristics linked to a diagnosis of hypomagnesaemia will serve to reduce possible morbidity and/or mortality due to associated maternal disease conditions like preeclampsia and preterm delivery. Objectives: The primary objective of this study was to determine the level of serum magnesium at which hypomagnesaemia could be diagnosed, while secondary objectives attempted to define maternal and fetal outcome due to hypomagnesaemia. Methodology: An initial pilot study was done to document the mean serum magnesium level for the population of patients attending UBTH. The main study was a prospective cohort study of antenatal women recruited in the second trimester and followed up till delivery and one week postpartum. Serum magnesium estimates were done with samples collected at recruitment and thereafter, at delivery. The magnesium levels determined were used to divide the subjects into two groups of hypomagnesaemic and normomagnesaemic patients. Their sociodemographic and clinical characteristics were used to generate a database for analysis