116: The impact of a preterm singleton delivery upon a subsequent twin gestation

Abstract

GESTATION FRANCESCA FACCO, KATE NASH, WILLIAM GROBMAN, Northwestern University, Chicago, Illinois OBJECTIVE: To determine whether preterm birth of a singleton is associated with an increased risk of preterm birth in a subsequent twin pregnancy. STUDY DESIGN: All patients who delivered a singleton followed by a twin pregnancy at Northwestern Memorial Hospital between 6/1/1995 to 5/31/2005 were identified. Those women with a preterm delivery (less than 37 weeks) prior to the index pregnancies, who delivered the index twin or singleton pregnancy prior to 20 weeks, iatrogenically preterm, or with a major fetal anomaly were excluded from further analysis. The group was then analyzed using a cohort study design, in which those whose singleton delivery was preterm were compared with those whose singleton delivery was term. Bivariable comparisons were made with the student t test and chi square analysis, and multivariable logistic regression was also utilized. RESULTS: Three hundred and three women were identified who delivered a singleton followed by twins. Twenty-four (7.9%) of the initial singletons deliveries were preterm. The women who delivered preterm singletons were no different from those who delivered term singletons with regard to age, significant past medical history, or number of prior term births, although they were more likely to be from a non-Caucasian ethnic group (P .01). Also, women who had delivered a preterm singleton pregnancy were significantly more likely than those who had delivered a term singleton pregnancy to deliver a subsequent preterm twin pregnancy (75.0% versus 46.2%, odds ratio 3.5, 95% confidence internal 1.3 to 9.1). This significant difference persisted in multivariable analysis after controlling for ethnicity (adjusted odds ratio 3.3, 95% confidence interval 1.3, 8.6). CONCLUSION: Preterm birth of a singleton is associated with a significantly increased risk of preterm birth in a subsequent twin gestation.