Blood lead and mercury levels in pregnant women in the United States, 2003-2008.

Chemical exposure during pregnancy is potentially harmful to the developing fetus, as the placenta cannot protect against heavy metals such as lead and mercury. Cord blood mercury levels have been associated with childhood cognitive function. High levels of lead exposure during pregnancy have been associated with adverse birth outcomes and, in some studies, with lower cognitive function test scores in childhood; relatively low lead levels have recently been associated with a small risk of decreased birthweight. While intervention for pregnant women with blood lead levels greater than or equal to 5 μg/dL has been recommended, no comparable recommendation for blood mercury in pregnant women has been established.This report presents geometric mean lead and mercury blood levels of pregnant women in the United States based on using the 2003-2008 National Health and Nutrition Examination Surveys (NHANES). Throughout this report, the term mean refers to the geometric mean.