A stratified, prospective cohort analysis was completed on 1,203 African American, Hispanic, and White women. All women were assessed for abuse at the first prenatal visit and twice more during pregnancy. They were also assessed for risk factors of low birth weight using Institute of Medicine correlates. Prevalence of physical or sexual abuse during pregnancy was 16% (1 of 6). Abused women were twice as likely to begin prenatal care during the third trimester, with abuse preceding late entry. Abuse was recurrent, with 60% of the women reporting repeated episodes. More severe abuse was significantly correlated with lower infant birth weights for all three ethnic groups. Abuse during pregnancy was a significant risk for low birth weight as well as maternal low weight gain, infections, anemia, smoking, and use of alcohol and drugs. When compared to women who were not abused, women abused during pregnancy delivered infants averaging 133 g less. Abused White women delivered infants with the greatest reduction in birth weight.