500-mg Calcium Pill Protects Against Preeclampsia, Researchers Say

 Taking 500 mg of calcium a day reduces the likelihood of pregnant women developing preeclampsia in pregnant women as much as higher doses, according to a study in The New England Journal of Medicine published on January 11. 

The study also shows that the lower dose of calcium protects against preterm birth almost as well as the higher dose recommended by the World Health Organization (WHO). 

Preeclampsia complicates up to 8% of pregnancies and may contribute to 45,000 maternal deaths globally every year. The US Centers for Disease Control and Prevention estimates that preeclampsia occurs in about 1 in 25 pregnancies, and Black women are 60% more likely to develop the condition than are White women.

Calcium supplementation reduces the risks for preeclampsia, per WHO guidelines. 

The WHO has recommended between 1500 mg and 2000 mg of calcium supplementation daily along with one 30-60 mg iron pill for pregnant women who receive insufficient calcium in their diets, which the WHO says generally occurs in lower-income nations and not wealthier nations, such as the United States. 

This dosage amounts to a minimum of three calcium pills per day because the dietary supplements generally come from suppliers in 500-mg doses. Researchers say the supplements are too expensive for many health authorities of low- and middle-income nations to provide, and that taking so many pills presents a barrier to use even if they were plentiful. In countries such as Tanzania and India, Sudfeld explained, governments generally distribute supplements like calcium for free at health clinics.

The WHO recommendation is "not implemented many places," said study author Christopher Sudfeld, ScD, associate professor of global health and nutrition at Harvard University's T.H. Chan School of Public Health, in Boston. Due to the cost, Tanzania has never implemented WHO's calcium recommendation, Sudfeld said, providing only the iron pill. 

The randomized double-blinded study included 11,000 pregnant women in Tanzania and 11,000 pregnant women in India. None had yet given birth, which increased their risk for preeclampsia. All participants were older than 18 years and were less than 20 weeks pregnant, according to their most recent menstrual date. Half of participants received the three daily 500-mg calcium pills recommended by WHO; the other half received a single calcium pill and two placebo pills. 

Researchers measured blood pressure and urine protein levels starting at 20 weeks of gestation, at delivery, and 6 weeks after giving birth. 

Regardless of how much calcium people consumed daily, preeclampsia occurred approximately 3% of both the 500-mg and 1500-mg groups. Similar rates of preterm births occurred in both groups, although in Tanzanian, women in the 500-mg arm were somewhat more likely to give birth early. 

"We're working with governments but we're also going to disseminate the results to WHO, so that they can do their process for the next antenatal care guidelines, to potentially change the global guidelines," to support a lower calcium supplement target, Sudfeld said. 

Does Calcium Actually Prevent Preeclampsia?

But Ahizechukwu Eke, MD, PhD, MPH, a pharmacologist who practices maternal fetal medicine at Johns Hopkins Medicine in Baltimore, questioned whether calcium really works to prevent preeclampsia. 

Eke said that the causes of preeclampsia are multifactorial, and researchers have yet to definitively demonstrate the mechanism of action by which calcium works to prevent the condition. One hypothesis is that calcium reduces the amount of contractions in a woman's uterus, thereby lowering blood pressure. 

Low-dose aspirin is also used to prevent preeclampsia, and Eke said that the pharmacokinetic pathway by which this drug inhibits preeclampsia is more clear.

"I'm not saying we should stop using calcium, far from it," Eke said. But as calcium supplementation to prevent preeclampsia continues, Eke called for pharmacokinetic studies to explore whether and how calcium works.

Sudfeld and Eke report no relevant financial relationships.

https://www.medscape.com/viewarticle/calcium-pill-500-mg-protects-against-preeclampsia-2024a10000p9