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APHA Scientific Session and Event Listing

Marie Lynn Miranda, PhD, Children's Environmental Health Initiative, Duke University, Box 90328, Durham, NC 27708-0328, 919-613-8023, mmiranda@duke.edu, Geeta Swamy, MD, Dept. of Obstetrics & Gynecology, Division of Maternal-Fetal Medicine and Division of Clinical and Epidemiological Research, Duke University Medical Center, Box 3967, Durham, NC 27710, Betsy Enstrom, Insitute of Statistics and Decision Sciences, Duke University, 214 Old Chemistry, Box 90251, Durham, NC 27708, and Alan Gelfand, PhD, Institute of Statistics and Decision Sciences, Duke University, 223A Old Chemistry Building, Box 90251, Durham, NC 27708.

Although birthweight appears to increase with maternal age and parity, previous analyses have not systematically disentangled the two phenomena. Using 2003 North Carolina Detailed Birth Record Data, we examined the joint influence of maternal age and parity on birthweight. Multivariate linear modeling was used to determine the relative contribution of advancing maternal age and birth order to birthweight, controlling for gestational age, infant sex, marital status, race/ethnicity, and education. The analysis was limited to 65,293 singleton, non-anomalous, term live births without maternal medical conditions or tobacco use. Maternal age was stratified into 5-year intervals from 15 to 44 years. Subjects were divided into (and further limited to) non-Hispanic whites, Hispanics, and non-Hispanic blacks. Maternal age and birth order were significant (p<.0001) predictors of birthweight, with the largest increase occurring between first and second births and with birthweight rising into the 30-34 year maternal age range. Controlling for potential confounders, birth order appears more influential on birthweight than maternal age. Our analysis indicates first-born blacks are smaller and the incremental gain in birthweight among second-born blacks is also smaller, as compared to whites. Maternal age is more complicated in that incremental gain in birthweight for blacks is virtually flat through age 20, and is quite steep for whites; the relative incremental gains follow a complicated pattern thereafter. These results are consistent with the weathering hypothesis. Understanding not only factors contributing to birthweight but also the interaction of such factors may lead to identifiable markers and interventions against low birthweight.

Learning Objectives:

• 1.Discuss the relationship between maternal age, birth order and birthweight.
• 2.Understand racial difference in birthweight patterns.
• 3.Consider the research results within the context of the weathering hypothesis.

Presenting author's disclosure statement:

Not Answered