Low pregnancy weight gain and small for gestational age: a comparison of the association using 3 different measures of small for gestational age.

Abstract

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. This was a retrospective cohort study of 104,980 singleton, term births from the 2000-2005 Pregnancy Risk Assessment Monitoring System (PRAMS). 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. Associations between low PWG and SGA varied little by definition of SGA and contributed to only a small proportion of term SGA infants.