Objective: To evaluate the association between maternal reproductive history and preterm delivery.
Methods: The 312 preterm delivery cases, studied in aggregate, and 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 very preterm delivery [gestational age at delivery <34 weeks]), were compared with 424 randomly selected women who delivered at term. Maternal medical records provided information on maternal reproductive history, pregnancy outcome, as well as sociodemographic characteristics. Using multivariate logistic regression, we derived maximum likelihood estimates of adjusted odds ratios (OR) and 95% confidence intervals (CI).
Results: A history of 2+ miscarriages was (OR = 2.2; 95% CI 1.2-3.9), but a history of 2+ prior induced abortions (OR = 1.2; 95% CI 0.7-2.0) was not, associated with preterm delivery in the index pregnancy. Analyses of preterm delivery subgroups indicated that a history of 2+ miscarriages was associated with an increased risk of spontaneous preterm labor (OR = 2.6; 95% CI 1.2-2.8), preterm premature rupture of membrane (OR = 1.8; 95% 0.7-4.4), and medically induced preterm delivery (OR = 1.9; 95% CI 0.8-4.2), though only the former approached statistical significance. Excess risk of preterm delivery was associated with maternal prior history of delivering a stillborn infant (OR = 10.7), a prior history of delivering a newborn that later died during the neonatal period (OR = 3.2), and a prior history of having a pregnancy complicated by spontaneous preterm delivery (OR = 6.0). Generally these associations were evident for each subgroup of preterm delivery, though inferences were often hindered by our relatively small sample size.
Conclusions: These results support the hypothesis that maternal adverse reproductive history is associated with an increased risk of preterm labor and delivery.