June 07, 2017
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Calcium supplementation in pregnancy associated with sex-specific childhood bone development

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In a rural African community where calcium intake is low, maternal calcium supplementation during pregnancy was associated with childhood growth and bone development at ages 8 to 11 years, according to study findings published in Bone.

“The importance of adequate dietary calcium intakes for healthy skeletal growth has long been recognized,” Kate Anna Ward, PhD, a senior investigator scientist with the Medical Research Council Elsie Widdowson Laboratory in Cambridge, United Kingdom, and colleagues wrote. “Despite this, many trials have not shown significant effects of [calcium] supplementation on bone growth and mineralization, and those that have shown effects often do not have a sufficient follow-up period to determine whether the effects are sustained. One reason for this may be that the trials are mostly conducted in countries where intakes are, on average, in alignment with dietary recommendations. Less is known from populations where habitual [calcium] intakes are low.”

Ward and colleagues analyzed data from 447 Gambian children of mothers who participated in a calcium supplementation trial during pregnancy. Mothers in the study received either 1,500 mg of calcium carbonate or matching placebo from 20 weeks’ gestation until term; children were assessed between the ages of 8 to 12 years (mean age, 9 years). Researchers measured height-for-age z scores, mid-upper arm circumference and triceps skinfold thickness; bone and body composition were measured via DXA; measurements of the distal and diaphyseal tibia were obtained via peripheral quantitative computed tomography. Researchers stratified the cohort by four sex–supplement groups: boys of mothers in the calcium supplement group; girls of mothers in the calcium supplement group; boys of mothers in the placebo group and girls of mothers in the placebo group.

Researchers observed sex-specific interactions based on calcium supplementation for height (P = .03), height-for-age z score (P = .02), weight (P = .01) and mid-upper arm circumference (P = .007), with results persisting after adjustment for current age and size in early life. Girls of mothers who received calcium supplementation were shorter and weighed less than girls born to mothers who received placebo. At the whole body, lumbar spine and tibia, girls born to mothers who received calcium supplementation had bones that were on average 2% to 4% smaller and containing 3% to 6% less bone mineral content vs. girls born to mothers who received placebo; these differences were not significant at the hip, but followed a similar pattern, according to researchers.

In contrast, boys born to mothers who received calcium supplementation tended to have bones that were on average 1% to 2% larger with 1% to 4% greater bone mineral content vs. boys born to mothers who received placebo; however, the differences did not rise to statistical significance.

“Despite being non-significant, it is noteworthy that the differences between the supplement groups in [boys] were in the opposite direction to those in [girls] and in the same direction as those in the anthropometric variables,” the researchers wrote.

For DXA-measured outcomes, researchers observed a sex-specific supplementation effect for fat mass (P = .02); girls born to mothers who received calcium had less fat mass than girls born to mothers who received placebo (P = .3), and boys born to mothers who received calcium had greater fat mass than boys born to mothers who received placebo (P = .02).

The researchers noted that the study is a post-hoc analysis of a trial designed to detect differences in maternal preeclampsia rates and infant growth in response to calcium supplementation, and was not designed to test sex-specific differences. – by Regina Schaffer

Disclosure: The researchers report no relevant financial disclosures.