Insufficient Calcium in Pregnancy Boosts Lead in Blood
Suzanne Rostler / Reuters Health 7nov00

NEW YORK - Pregnant women who do not consume enough calcium may be at risk for more than thinning bones. According to recent findings, pregnant women who did not get enough calcium had higher levels of lead in their blood compared with women who did have adequate calcium intake.

However, overall levels of lead in the blood remained low--less than 5 micrograms (mcg) per deciliter (dL) of blood. Levels above 10 mcg/dL are considered cause for concern, Dr. Irva Hertz-Picclotto, the study's lead author, told Reuters Health.

"At this point, there are no data on the harm from these low levels, either to the mother or the fetus," said Hertz-Picclotto, from the University of North Carolina in Chapel Hill. "Nevertheless, we do know that lead is passed easily to the fetus ... and many studies have already shown that children with higher lead levels have deficits in cognitive development as well as behavioral problems."

The findings, based on interviews and blood samples from 195 pregnant women, are published in the November issue of the American Journal of Epidemiology.

During pregnancy and lactation, the calcium stored in the mother's bone is mobilized to help form the fetal skeleton and produce milk. Pregnant women who do not consume enough calcium may release more of the mineral from their bones, and as calcium is released, so is lead.

The investigators found that blood lead levels rose higher in older women compared with younger women, possibly because they had accumulated more lead in their bones over the years.

During the second half of pregnancy, when lead stored in bone tissue is released into the blood, blood lead levels increased by 25% in women with low calcium intake who were aged 18. In comparison, 23-year-olds had an increase of 37% and 33-year-olds had an increase of 65%. The lead level nearly doubled in 43-year-olds with low calcium intake, who had an increase of 99%.

In other findings, older women, black women and those who smoked and had lower educational levels had higher blood lead levels during pregnancy. Women with a history of breast-feeding and those with a higher calcium intake had lower blood lead levels.

"Pregnant women need adequate calcium to prevent mobilization into the blood of lead that has been stored in bone. Since lead will reach the fetus, a high intake of calcium means the newborn begins life with a lower lead burden," Hertz-Picclotto said. "Quitting smoking will also minimize the lead burden to the infant."

SOURCE: American Journal of Epidemiology 2000;152:829-837