Randomized clinical trial with magnesium supplementation during pregnancy

João Guilherme Bezerra Alves

Director of Education and Coordinator of the Graduate Program at the Professor Fernando Figueira Institute of Integral Medicine (IMIP), Recife (PE)

Project name

Randomized clinical trial with magnesium supplementation during pregnancy


The study tested the effectiveness of magnesium citrate tablets as a way to prevent premature birth. Easily and cheaply manufactured, they could work as a low-cost option to reduce prematurity, especially in countries with limited resources.

How was the experiment

The team assembled a cohort of 1,031 pregnant women receiving prenatal care from three hospitals in Pernambuco state: IMIP, in Recife, Dom Malan, in Petrolina, and Petrolina Campos, in São Lourenço da Mata. Excluding refusals, 911 women agreed to participate. Using a randomized, double-blind trial, 449 received magnesium citrate tablets, which costs 17 cents of reais each, and 462 received a placebo. Each pregnant woman took 300 mg of magnesium citrate daily from the 20th week until the end of pregnancy. During prenatal consultations, held every 2-4 weeks, researchers collected blood for routine examinations and dosed the magnesium. Approximately 30 percent of pregnant women had magnesium deficiency at the time of admission to the study, which declined with advancing gestational age.

Main results

With respect to the main outcome, the study demonstrates that magnesium citrate does not offer a protective or preventive effect for premature birth, although the rate of prematurity in this cohort was lower (7 percent) than local and national indicators, which is 11.5 percent. Using logistic regression models, with adjustments for socioeconomic, demographic, environmental, obstetric, and anthropometric risk factors, the researchers found no difference between the two groups with respect to adverse perinatal (premature birth, stillbirth, and small for gestational age) or maternal (pre-eclampsia, premature detachment, and placental hypertension) outcomes. However, there was a significant association between the use of oral magnesium and neonatal mortality, with 0.6% of deaths in the intervention group and 2.9% in the control group. The fact that these pregnant women had different and more welcoming prenatal care, associated with home visits and personalized telephone service, may have influenced these positive outcomes.

Why is it innovative

It was the first time that the administration of magnesium citrate was evaluated in Brazil as a preventive measure against prematurity.

Problem that solves

According to a survey by the National School of Public Health (ENSP / Fiocruz) in 2016, 11.5 percent of births in Brazil are premature. According to the IBGE, 2.87 million births were registered in Brazil in 2017, which means that, on average, about 330 thousand babies are born before 37 weeks.

Solution cost

According to a study by the Health Management and Evaluation Research Group at the IMIP, the average cost of prenatal care in the Family Health Program is R$ 39,226.88 per Health Unit.

Implications for the brazilian health system

The study reinforced the importance of ensuring quality prenatal care not only to avoid and reduce costs associated with premature births, but also to promote better monitoring and health of pregnant women. Quality prenatal care already provides an element of protection.

Implications for global health

The study also reinforces the importance of quality prenatal care for the international scientific community.

Next steps

It would be interesting to investigate the possible effects of higher doses of magnesium, to verify the influence of the mineral in the reduction of neonatal mortality, and to repeat the same research with calcium.

Article about the project

The study that evaluated magnesium, but found that quality prenatal care is what can decrease premature births

Because it is indispensable in several body processes, magnesium is among the four most important mineral salts for human health. During pregnancy, magnesium deficiency can cause complications that lead to premature birth, such as pre-eclampsia, sudden increase in blood pressure, and other vascular problems in the placenta, such as detachment. The objective of a study […]
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