Risk of Low Birth Weight Associated with Advanced Maternal Age Among Four Ethnic Groups in the United States

Objectives: To examine and compare the risk of low birth weight associated with delayed childbearing in four ethnic groups using nationally representative data in the United States. Methods: We compared the risk of low (<2.5 kg) birth weight among African Americans, Mexican Americans, Puerto Ricans, and non-Hispanic whites using birth data for the United States obtained from the National Center for Health Statistics. Comparisons were done separately for first births and births of second or higher order and in terms of odds ratios, risk differences and attributable fractions of very low (<1.5 kg), middle low (1.5–2.5) and overall low birth weight. Statistical analysis included use of logistic regression models with likelihood ratio tests for interaction effects. Results: African Americans and Puerto Ricans, and to a lesser extent Mexican Americans, had higher risk differences associated with advanced maternal age. For first births, the risk differences associated with advanced maternal age (≥35 years) in low birth weight were 5.3% (95% CI, 4.7–6.0), 4.3% (95% CI, 1.7–6.9), and 3.7% (95% CI, 2.8–4.5) for African Americans, Puerto Ricans, and Mexican Americans, respectively, as compared with 2.6% (95% CI, 2.4–2.7) for non-Hispanic whites. On the other hand, the odds ratios associated with advanced maternal age were more similar across the four ethnic groups. Differences were greater for all ethnic groups in the case of first births as compared with births of second or higher order. Conclusions: Advanced maternal age appears to be associated with for the most part similarly increased odds of low birth weight for African Americans, Mexican Americans, Puerto Ricans, and non-Hispanic whites. However, the age-related increments in the risk of low birth associated with advanced maternal age are greater for African Americans, Puerto Ricans and, to a lesser extent, Mexican Americans, as compared with non-Hispanic whites.