Likelihood of ET 3 vs. 1-2 , FHB > 1 vs. 1 , and risks of preterm birth ( PTB , < 37weeks ' gestation ) , low birth weight ( LBW , < 2,500 g ) , and small-for-gestational-age birth weight ( SGA , < 10th percentile ) with FHB > 1 were modeled with binary logistic regression using a backward-stepping algorithm , and presented as adjusted odds ratios ( 95 % confidence intervals ) .