Contributions of ischaemic placental disease to preterm birth in twin gestations

To evaluate the extent to which ischaemic placental disease (IPD)--defined as women or newborns diagnosed with pre-eclampsia, small for gestational age (SGA), or abruption, is associated with preterm birth in twin gestations.

A population-based study of women who delivered twin live births and stillbirths at 20-44 weeks gestation from 1995-2004 in the US was performed (n=1,105,666). We compared the frequency of IPD in term and preterm (<37 weeks) twin births. SGA was defined as twins with birthweight<10th percentile for gestational age, and corrected for infant sex. The association between IPD and preterm birth was expressed as hazard ratio, derived from Cox proportional hazard regression models after adjusting for potential confounders.

The overall rate of twin preterm birth was 57%. IPD was present in 20% of twin preterm births in comparison to a rate of 16% at term. Both pre-eclampsia and abruption, but not SGA, were associated with increased preterm birth rates. Women with two or more of the IPD conditions were more likely to deliver at preterm than at term gestations.

In comparison to twin births delivered at term, IPD is more common in preterm births. Efforts to understand the role of IPD in twin gestations based on preterm birth subtypes may reveal important insights.