Excessive birthweight is a growing concern and challenge in current obstetrics, and has been associated with perinatal complications, such as shoulder dystocia, and long-term health complications such as type 2 diabetes. (1-3) Variation of birthweight measures used to describe excessive birthweight contributes to the lack of consensus in the literature. In addition, these measures do not allow for the study of the effect of Physical Activity (PA) at non-traditional points in the distribution. The effect of PA may not be found at mean birthweight estimates, but an effect may be present above the 70th percentile of birthweight z-scores standardized for infant sex and gestational age.(4) We hypothesized that women who performed 150 minutes or more of PA per week on average would have lower odds of delivering a neonate whose birthweight z-score was above the 70th percentile of the sample’s birthweight z-score compared to the neonates of women who were sedentary. We also sought to replicate findings that birthweight z-score varies by PA category above the 70th percentile of birthweight z-score using a sample in which PA behavior data was collected prospectively.(4) We used data from the Archives for Research on Childhood Health cohort. We calculated birthweight z-score and trichotomized PA. We used multivariable logistic regression to model the association between PA measured early in pregnancy and birthweight z-score above the 70th percentile. This study did not support the hypothesis that the odds of delivering a neonate above the 70th percentile would be lower for women who performed 150 minutes or more of PA per week compared to the neonates women who were sedentary.
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