Effects of calcium supplementation on pregnancy-induced hypertension

To the Editor. —The meta-analysis of calcium supplementation and pregnancy-induced hypertension and preeclampsia by Bucher et al1is the fourth to be performed in recent years using the same basic data and indicating a large overall reduction in risk due to calcium supplementation.1-4Although these optimistic results are useful for generating hypotheses and for assessing the available evidence, inferences about treatment may be misleading. Two of the 9 studies in the recent meta-analysis1were not peer reviewed and are difficult to evaluate since 1 was published as an abstract and a brief submission to a conference proceedings (Montanaro et al, 1987 and 1990), another as a letter to the editor (Lopez-Jaramillo et al, 1990). A third trial (Villar et al, 1987) was cited by the meta-analysis both for preeclampsia and gestational hypertension with identical odds ratios and confidence intervals for each. Even most of the full-length publications do not specify whether