The Effect of Calcium Supplementation on Body Weight Before and During Pregnancy in Women Enrolled in the WHO Calcium and Preeclampsia Trial.

Introduction: Obesity is a major and challenging public health problem. The aim of this substudy is to evaluate the effect of calcium supplementation on body weight in women recruited in the Calcium and Preeclampsia trial. Methods: Women were recruited before pregnancy and randomized to receive a calcium supplement containing 500 mg of elemental calcium or placebo until 20 weeks' gestation; all women received 1.5 g from 20 weeks until delivery. Results: A total of 630 women conceived during the study, 322 allocated to calcium and 308 to placebo. Among these, 230 allocated to calcium and 227 allocated to placebo had information on body weight at baseline and at 8 weeks' gestation. During the study period, women allocated to calcium had a mean weight increase of 1.1 (SD +/- 5.5) kg, whereas those allocated to placebo had a mean increase of 1.5 (SD +/- 6.1) kg, a mean difference of 0.4 kg (95% -0.4 (-1.4 to 0.6); P = .408). Women classified as obese at the start of the trial had a lower body weight gain at 8 weeks' gestation (1.0 kg; 95% CI: -3.2 to 1.2; P = .330) and at 32 weeks' gestation (2.1 kg; 95% CI: 5.6-1.3; P = .225) if they received calcium as compared to placebo. However, none of these differences were statistically significant. Conclusion: The smaller increase in body weight found in women supplemented with 500 mg elemental calcium daily is quantitatively consistent with previous studies. However, in this study, the difference was not statistically significant.