Introduction
Childbearing during adolescence and young adulthood is associated with adverse effects on health and quality of life. Lowering birth rates among young women is a binational priority in the US-Mexico border region, yet baseline information about birth rates and pregnancy risk is lacking. Increased understanding of the characteristics of young women who give birth in the region will help target high-risk groups for sexual and reproductive health services.

Methods
We examined data on reproductive health characteristics collected in hospitals from 456 women aged 24 years or younger who gave birth from August 21 through November 9, 2005, in Matamoros, Tamaulipas, Mexico, and Cameron County, Texas. We calculated weighted percentages and 95% confidence intervals (CIs) for each characteristic and adjusted odds ratios (AORs) for Matamoros and Cameron County women by using multiple logistic regression techniques.

Results
Numbers of births per 1,000 women aged 15 to 19 years and 20 to 24 years were similar in the 2 communities (110.6 and 190.2 in Matamoros and 97.5 and 213.1 in Cameron County, respectively). Overall, 38.5% of women experienced cesarean birth. Matamoros women reported fewer prior pregnancies than did Cameron County women and were less likely to receive early prenatal care but more likely to initiate breastfeeding. Few women smoked before pregnancy, but the prevalence of alcohol use in Cameron County was more than double that of Matamoros. In both communities combined, 34.0% of women used contraception at first sexual intercourse.

Conclusion
Despite geographic proximity, similar ethnic origin, and comparable birth outcomes, young Mexican and US women showed different health behavior patterns. Findings suggest possible pregnancy prevention and health promotion interventions.