Recurrent Preterm Birth in Utah

In multiparous women, history of preterm birth is a risk factor for recurrence. We examined patterns of recurrent preterm birth by clinical presentation and additional risk factors for recurrence among 76,657 women who had their first three singleton live births in Utah, 1989- 2007. We also evaluated the association between gestational weight gain and preterm birth using a bidirectional case-crossover study to control for genetics and other time-invariant characteristics. Unadjusted and multivariable-adjusted logistic regression, multinomial regression, and conditional logistic regression were used to calculate odds ratios (OR). In our study women were likely to experience recurrent preterm birth of the same clinical subtype; however, recurrence of other clinical subtypes was also common. The highest odds of recurrence were in women with two prior preterm births of the same subtype. Additional risk factors for recurrence included a short interpregnancy interval, the presence of a preexisting maternal medical condition, history of a birth at 28-32 weeks gestation, and the presence of a fetal anomaly on the birth record for the current live birth. Risk factors varied depending upon the clinical subtype of the most recent preterm birth. Finally, we found that women who gained more weight than recommended during pregnancy were at risk for indicated preterm birth while those who gained less than recommended were at risk for spontaneous preterm birth.