Calcium Supplementation for Lead Reduction

We recruited pregnant women from 2001 through 2003 at the Mexican Social Security Institute (Instituto Mexicano del Seguro Social) pre-natal clinics that serve a low- to moderate-income population in Mexico City. We assessed 3,836 women for eligibility, of whom 1,981 did not meet study eligibility criteria (pregnancy of no more than 14 weeks’ gestation; not presenting with a high-risk pregnancy; plans to reside in the metropolitan Mexico City area for ~ 5 years) or had other reasons not being enrolled (n = 2). Of the remaining 1,853 eligible women, 670 (36%) agreed to participate and signed the informed consent, and were randomly assigned to receive a daily supplement of 1,200 mg calcium [two 600-mg calcium carbonate tablets (Wyeth Consumer Health Care/Lederle Laboratories, Inc., México City, México) at bedtime; n = 334] or placebo (n = 336). We assessed blood lead levels, dietary calcium intake, and reported use of lead-glazed ceramics (LGC) at three time points: baseline (first trimester), 6 months (second trimester), and 8 months (third trimester). We assessed compliance by pill count at each follow-up visit. We defined women who had at least one blood lead measurement at 6 or 8 months’ gestation (n = 565; 84%) as having completed follow-up. Eight women did not have baseline blood lead levels, yielding a total of 557 subjects (83%) available for inclusion in the final analyses (Figure 1).
The research protocol was approved by the Human Subjects Committee of the National Institutes of Public Health, the Mexican Social Security Institute, the Brigham and Women’s Hospital, and the Harvard School of Public Health and complied with both Mexican and U.S. federal guidelines governing the use of human participants. All participating mothers received a detailed explanation of the study intent and procedures and were advised on identifying and avoiding LGC pottery use during pregnancy before signing the approved written informed consent.