Objective: The purpose of this study was to assess associations between pregnancy weight gain (PWG) and small for gestational age (SGA) defined by birthweight < 10th percentile and 2 more restrictive definitions and to assess the proportion of SGA attributed to low PWG.
Study design: This was a retrospective cohort study of 104,980 singleton, term births from the 2000-2005 Pregnancy Risk Assessment Monitoring System (PRAMS).
Results: Compared with women who gained 15-25 lbs during pregnancy, women who gained 1-14 lbs had 1.5 greater odds (95% confidence interval, 1.2-1.8) of SGA for the most restrictive definition and 1.2 greater odds (95% confidence interval, 1.1-1.4) for the least restrictive definition, after adjustments for confounders. Depending upon the definition used, PWG below current Institute of Medicine recommendations contributed to 10-15% of SGA, representing 0.8-1.2% of all singleton term infants.
Conclusion: Associations between low PWG and SGA varied little by definition of SGA and contributed to only a small proportion of term SGA infants.