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Health News Archive 367 - Pregnancy
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Calcium Can Reduce Hypertension and Preeclampsia During Pregnancy

An increased intake of calcium may reduce the risk of hypertension and preeclampsia during pregnancy, according to a new review of clinical trials.

The review, published in the Cochrane Database of Systematic Reviews, looks at 12 randomized controlled studies, one involving over 4,000 pregnant women in North America, and one study conducted by the WHO involving over 8,000 women internationally. “Pregnant women from communities with low dietary calcium who received at least 1.5 grams per day of calcium by mouth during the second half of pregnancy had a lower risk of hypertension and preeclampsia, and of severe complications including death, than women who received placebo treatment,” said lead review author Dr. G.J. Hofmeyr.

In January 2002, the American College of Obstetricians and Gynecologists issued the following statement: “Daily calcium supplementation has not been shown to prevent preeclampsia and, therefore, is not recommended.” But the new review may change the minds of some physicians because it is based on data not available in 2002. “The review is likely to convince health providers of the need to ensure that pregnant women have adequate calcium intake,” Hofmeyr said.

Abstract

BACKGROUND: Pre-eclampsia and eclampsia are common causes of serious morbidity and death. Calcium supplementation may reduce the risk of pre-eclampsia through a number of mechanisms, and may help to prevent preterm labor.

OBJECTIVES: To assess the effects of calcium supplementation during pregnancy on hypertensive disorders of pregnancy and related maternal and child outcomes.

SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group Trials Register (February 2006), the Cochrane Central Register of Controlled Trials (The Cochrane Library, 2005, Issue 4), and contacted study authors.

SELECTION CRITERIA: Randomized trials comparing at least one gram daily of calcium during pregnancy with placebo.

DATA COLLECTION AND ANALYSIS: We assessed eligibility and trial quality, extracted and double-entered data.

MAIN RESULTS: Twelve studies of good quality were included. The risk of high blood pressure was reduced with calcium supplementation rather than placebo (11 trials, 14,946 women: relative risk (RR) 0.70, 95% confidence interval (CI) 0.57 to 0.86). There was also a reduction in the risk of pre-eclampsia associated with calcium supplementation (12 trials, 15,206 women: RR 0.48, 95% CI 0.33 to 0.69). The effect was greatest for high-risk women (5 trials, 587 women: RR 0.22, 95% CI 0.12 to 0.42), and those with low baseline calcium intake (7 trials, 10,154 women: RR 0.36, 95% CI 0.18 to 0.70).The composite outcome maternal death or serious morbidity was reduced (4 trials, 9732 women; RR 0.80, 0.65 to 0.97). Almost all the women in these trials were low risk and had a low calcium diet. Maternal deaths were reported in only one trial. One death occurred in the calcium group and six in the placebo group, a difference which was not statistically significant (RR 0.17, 95% CI 0.02 to 1.39).There was no overall effect on the risk of preterm birth (10 trials, 14,751 women: RR 0.81, 95% CI 0.64 to 1.03), or stillbirth or death before discharge from hospital (10 trials 15,141 babies; RR 0.89, 95% CI 0.73 to 1.09). Blood pressure in childhood has been assessed in one study: childhood systolic blood pressure greater than 95th percentile was reduced (514 children: RR 0.59, 95% CI 0.39 to 0.91).

AUTHORS' CONCLUSIONS: Calcium supplementation appears to almost halve the risk of pre-eclampsia, and to reduce the rare occurrence of the composite outcome 'death or serious morbidity'. There were no other clear benefits, or harms.

Source: Hofmeyr G, Atallah A, Duley L. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems. Cochrane Database Syst Rev. 2006 Jul 19;3:CD001059.

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