Serum calcium and magnesium levels in women presenting with pre-eclampsia and pregnancy-induced hypertension: a case–control study in the Cape Coast metropolis, Ghana

BACKGROUND Hypertensive disorders of pregnancy are important causes of morbidity and mortality. The levels of calcium (Ca2+) and magnesium (Mg2+) in pregnancy may implicate their possible role in pregnancy-induced hypertension. This study assessed serum Ca2+ and Mg2+ levels in women with PIH (pregnancy-induced hypertension) and PE (pre-eclampsia), compared to that in normal pregnancy. METHODS This case-control study was conducted on 380 pregnant women (≥20 weeks gestation) receiving antenatal care at three hospitals in the Cape Coast metropolis, Ghana. This comprised 120 women with PIH, 100 women with PE and 160 healthy, age-matched pregnant women (controls). Demographic, anthropometric, clinical and obstetric data were gathered using an interview-based questionnaire. Venous blood samples were drawn for the estimation of calcium and magnesium. RESULTS Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were significantly raised in women with PIH (p < 0.0001) and PE (p < 0.0001). Women with hypertensive disorders (PE and PIH) had significantly lower serum calcium and magnesium levels than those in the control group (p < 0.0001 each). Of those with PIH, SBP correlated positively with BMI (r = 0.575, p < 0.01) and Ca2+ correlated positively with Mg2+ (r = 0.494, p < 0.01). This was similar amongst the PE group for SBP and BMI as well as for Ca2+and Mg2+ but was not significant. Multivariate analysis showed that women aged ≥40 years were at a significant risk of developing PIH (OR = 2.14, p = 0.000). CONCLUSION In this study population, serum calcium and magnesium levels are lower in PIH and PE than in normal pregnancy. Mineral supplementation during the antenatal period may influence significantly, the occurrence of hypertensive disorders in pregnancy.