Magnesium supplementation and perinatal hypoxia: outcome of a parallel group randomised trial in pregnancy.

ABSTRACT

OBJECTIVE: To determine the effects of magnesium supplementation in pregnancy on the incidence of hypoxic-ischaemic encephalopathy (HIE). DESIGN: A randomised double-blind placebo-controlled study. SETTING: A Midwife Obstetric Unit and its two referral hospitals in Cape Town, South Africa. POPULATION A group of 4494 black pregnant women of low socio-economic status. METHOD: Mothers, from the time of booking until delivery, were randomised to receive two identical tablets daily, containing either 128 mg slow-release magnesium stearate or lactose sugar. MAIN OUTCOME MEASURES: Primary The incidence of HIE. Secondary The incidence of fetal heart rate decelerations, term Stillbirths, Low Apgar Scores, Meconium Aspiration Pneumonia. RESULTS: The incidence of HIE (0.9%) was considerably less than anticipated (2%). There were 22 infants in the placebo group and 15 infants in the supplemented group (P = 0.279). The difference was not significant. Secondary outcomes such as late fetal heart rate decelerations (P = 0.002) and term stillbirths (P = 0.016) were reduced significantly in the supplemented group, but this finding needs further substantiation. CONCLUSIONS: Magnesium supplementation did not reduce the incidence of HIE significantly, probably because the study was underpowered and compliance was relatively poor.