Two recent studies emphasize just how sensitive the developing fetus is to substances absorbed or ingested by the mother.

Lead exposure. It's well established that children exposed to lead at early ages can experience neurologic and developmental problems. Now a study reports that exposure to lead during pregnancy-at levels much lower than previously considered dangerous-can have similar long-term effects. In the Mexico City Prospective Lead Study, researchers tracked the blood lead levels of women from 12 weeks of pregnancy until delivery. After birth, the children's blood lead level, IQ, and developmental scores were followed through age 10; researchers had complete data for 150 of the 321 children.

Higher maternal blood lead levels at 28 weeks' gestation were associated with lower child IQ. The sharpest drop in IQ measurements in children ages six to 10 occurred in those whose mothers' blood lead level increased from 1 to 6 micrograms per deciliter during the third trimester. This means the effects occurred below the "level of concern" the Mexican government and the Centers for Disease Control and Prevention set for intervention (10 micrograms per deciliter in pregnant women and children). The researchers suggest that the intervention level for lead in the blood be reevaluated in light of these findings.

ACE inhibitors. Because of their specific effects on fetal renal development, which takes place late in pregnancy, angiotensin-converting enzyme (ACE) inhibitors are contraindicated during the second and third trimesters. Now, however, a study has found that infants whose mothers had taken only an ACE inhibitor during the first trimester of pregnancy were at a 2.7 times increased risk for developing "major congenital malformations" than were infants born to women not taking antihypertensive medications. After adjusting for confounding variables, 7.12% of infants exposed to ACE inhibitors in the first trimester suffered a malformation, compared with only 2.63% of 29,096 infants whose mothers had not taken any antihypertensive medication. The abnormalities usually involved the cardio-vascular or central nervous system, and many infants suffered from more than one major malformation. Exposure to other types of antihypertensive medications in the first trimester did not carry a similar risk.

While these findings are drawn from small numbers and will need replication, they should be taken seriously. In a June 7 press release from the Agency for Healthcare Research and Quality, one sponsor of the study, agency director Carolyn Clancy, advises that "Clinicians who treat women of childbearing age and pregnant women should [horizontal ellipsis] consider whether to use other treatment options to control hypertension or kidney damage from diabetes."

Fran Mennick, BSN, RN