Calcium Supplements Help Babies' Bones in Calcium Deficient Women Nov. 29, 1999 (Atlanta) -- For pregnant women receiving low amounts of calcium in their diet, taking calciumsupplements averaging 1,300 mg a day during the second and third trimesters of pregnancy can increase the bone mineral content of their fetus by about 15%. However, according to a study in the October issue of the journal Obstetrics & Gynecology, for women who receive adequate calcium in their diets, calcium supplements are unlikely to result in much improvement in fetal bone mineralization. Babies born with better mineralization have stronger bones and a boost to their development.

This new study, done at the University of Tennessee in Memphis, involved 256 women in their fourth month of pregnancy. Half the women were given up to two grams of supplemental calcium carbonate per day while the others were given a placebo. The women were checked for the effects of the supplementation up until they gave birth. One week after birth, the infants underwent x-ray studies of their whole bodies to check for bone mineral content.

The results found that for mothers with the lowest rate of calcium intake (less than 600 mg per day), the total skeletal bone mineral content was significantly higher in infants of calcium-supplemented mothers compared to the calcium-deficient placebo group. The babies from mothers with adequate calcium in their diet, who were given supplements, had about the same mineral content as the mothers in their corresponding placebo group.

According to the lead author, Winston W. K. Koo, MD, now at Wayne State University/Hutzel Hospital in Michigan, supplementation's minimal effect on fetal bone mineralization in women with adequate dietary calcium intake may be due to a "maternal homeostatic response." In other words, the mother's body may protect the fetus by decreasing the absorption and retention of calcium at very high rates.

The results of the study do not mean women shouldn't take the supplements. Pregnant women do have additional calcium needs and the supplements provide for those needs. Rather, this new research shows that if the mother's diet provides adequate amounts of calcium and she also takes supplements, there is little or no effect on the fetus.