We are examining the role of maternal bone lead turnover during pregnancy and lactation as a potential source of lead exposure for the fetus and the infant (via breast milk). A cohort, ascertained at entry to care, consists of >1000 women to be followed through pregnancy. In the postpartum subjects are recruited for a nested case control study to assess the influence of lactation on maternal bone density, maternal blood lead and breast milk lead.

1. Positive pregnancy test, age 12-35 and informed consent;
2. Gestation <28 weeks at entry to prenatal care;
3. No history of serious chronic or metabolic diseases, which could affect maternal growth or bone density;
4. Not corticosteroid user or diagnosed use of illicit drugs;
5. Eligible for lactation study: Ascertainment during or participation in the pregnancy study and a negative pregnancy test.