Risk of preterm delivery in relation to maternal low birth weight

Objective. We examined the relationship between maternal low birth weight and preterm delivery risk. Methods. Information concerning maternal birth weight was collected during in-person interviews. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI). Preterm delivery cases were studied in aggregate, in subgroups (spontaneous preterm labor, preterm premature rupture of membranes, medically induced preterm delivery, moderate preterm delivery [gestational age at delivery 34-36 weeks], and early preterm delivery [gestational age at delivery <34 weeks]). Results. After adjusting for confounders, women weighing <2,500 g at birth had a 1.54-fold increased risk of preterm delivery versus women weighing =2,500 g (95% CI 0.97-2.44). Maternal low birth weight was associated with a 2-fold increased risk of spontaneous preterm delivery (95% CI 1.03-3.89), but weakly associated with preterm premature rupture of membranes (OR = 1.44; 95% CI 0.67-3.09) and medically induced preterm delivery (OR = 1.10; 95% CI 0.43-2.82). Maternal low birth weight was more strongly associated with early preterm delivery (OR = 1.94) than with moderate preterm delivery (OR = 1.46). Women weighing <2,500 g at birth and who became obese (pre-pregnancy body mass index, =30 kg/m(2)) before pregnancy had a 3.65-fold increased risk of preterm delivery (95% CI 1.33-10.02) versus women weighing =2,500 g at birth and who were not obese prior to pregnancy ( <30 kg/m(2)). Conclusions. Results confirm earlier findings linking maternal low birth weight with future risk of preterm delivery.