Pregnancy: Protecting Your Inner Child

Common chemicals inhaled or absorbed by expectant mothers can burden a child with lifelong learning and behavior problems, even infertility. Now, studies link mercury to premature births and milk to giving birth to twins.

Behavior ABCs

Tobacco smoke and lead harm the developing brain, but how many kids are affected? Whether mothers actively or passively inhale, prenatal exposure to tobacco smoke is linked to 270,000 U.S. cases of attention deficit hyperactivity disorder (ADHD), according to Bruce Lanphear, M.D., M.P.H., in a study published September 2006 online in Environmental Health Perspectives (EHP). Prenatal exposure to lead, found in pre- 1978 house paint and corroded plumbing, accounts for one-fifth (or 290,000) of all U.S. ADHD cases. "Our study demonstrates the tremendous human and economic cost of lead poisoning, even at low levels of exposure," says Lanphear, adding that the federal action level for lead in children's blood is not stringent enough to protect them. And lead does the greatest harm to neurodevelopment during the first trimester of pregnancy, according to a study in the November 2006 EHP.

Early Arrivals

On the rise in the U.S., premature delivery is a major cause of infant mortality. Smoking, alcohol, obesity, stress, poverty and illness are all risk factors. Yet premature births are often unexplained, says Diane Ashton, M.D., associate medical director at the March of Dimes. Methylmercury exposure may be another factor, according to a study published online September 2006 in EHP. Women living in Michigan who delivered very preterm babies (before 35 weeks) had higher levels of mercury in their hair. Higher levels of mercury in hair are associated with higher levels of fish consumption, says co-author Claudia Holzman, M.P.H, Ph.D. Holzman, however, notes fish are rich in heart-beneficial omega-3 fatty acids and pregnant women may want to consume moderate amounts, focusing on those with lower mercury levels.

Double Trouble

Twins suffer higher rates of premature birth, birth defects and pregnancy complications. In the U.S., roughly three twin sets are born per every 100 births, a rate that has escalated 31 percent from 1992 to 2001. Fertility treatments explain only some of this increase. Another possibility is recombinant bovine somatotropin (bST), given to cows to raise milk yields starting in the early 1990s. Vegans are only one-fifth as likely to give birth to twins as milkdrinkers, reports obstetrician Gary Steinman, M.D., Ph.D. in the May 2006 Journal of Reproductive Medicine. bST stimulates production of insulin-like growth factor (IGF), which accumulates in cows' milk. For people with a genetic tendency towards elevated IGF, consuming IGF in milk appears to enhance the chances of double ovulation and fraternal twins, says Steinman.