Gender-specific differences in birthweight and the odds of puberty: NHANES III, 1988-94.

The association between birthweight and the odds ratio (OR) of pubertal status in girls aged between 8 and 11 and in boys aged between 8 and 12 was examined using the 1988-94 Third National Health and Nutrition Examination Survey (NHANES III). Girls (n = 956), and boys (n = 1199), who had data on birthweight and Tanner staging were included. Maternal-reported birthweight, smoking in pregnancy and other information were provided in a home interview, while Tanner staging to assess pubertal status was part of a medical examination. Multiple logistic regression models were computed for the endpoints of the OR [95% confidence interval (CI)] of being Tanner Stage 2+ vs. 1 or being 2+ vs. 1 in an asynchronous pubertal pathway after adjustment for the complex sampling design of NHANES, age, race, height and body mass index (BMI). Birthweight was not associated with the OR of Tanner stage 2+ among girls; however, boys who were low birthweight (<2500 g) and boys born higher than average birthweight (3500-3999 g) were more likely to be Tanner stage 2+ than 1. Childhood BMI was associated with the OR of having entered puberty among girls, but not boys. In an analysis of asynchronous maturation, girls born at high birthweight (>4000 g) were more likely to have breast development 3+ than girls of normal birthweight, OR = 3.18 [95% CI 1.39, 8.25]. Thus, the birthweight-puberty association varies by gender and by pubertal pathway. Our findings need replication in prospective longitudinal studies, and research to understand the mechanisms underlying the relation of early life exposures to cancer risk.