Based on the approach of identifying covariates that produce adjusted ORs of 1 during the pre-influenza period, the group of covariates in the prematurity multivariate models included gestational age for first antenatal visit, maternal diabetes (gestational and/or non-gestational), multivitamin use in pregnancy, history of alcohol use during pregnancy, education less than 12th grade, and mother married. The covariates in the primary multivariate models for SGA included maternal age less than 19 y, maternal medical risk factors, labor/delivery complications, hypertension (treated or untreated), birth defects, and history of alcohol use during pregnancy.