title: Recurrence of preterm birth in singleton and twin pregnancies.
abstract: OBJECTIVE
  To assess recurrence of preterm birth and its impact on an obstetric population.
  
  
  METHODS
  Women with consecutive births at our hospital beginning with their first pregnancy were identified (n = 15,945). The first pregnancy was categorized as delivered between 24 and 34 weeks' gestation or 35 weeks or beyond, singleton or twin, and spontaneous or induced. The risk of preterm delivery in these same women during subsequent pregnancies was then analyzed.
  
  
  RESULTS
  Compared with women who delivered a singleton at or beyond 35 weeks' gestation in their first pregnancy, those who delivered a singleton before 35 weeks were at a significant increased risk for recurrence (odds ratio [OR] 5.6, 95% confidence interval [CI] 4.5, 7.0), whereas those who delivered twins were not (OR 1.9, 95% CI 0.46, 8.14). The OR for recurrent spontaneous preterm birth presenting with intact membranes was 7.9 (95% CI 5.6, 11.3) compared with 5.5 (95% CI 3.2, 9.4) with ruptured membranes. Of those women with a recurrent preterm birth, 49% delivered within 1 week of the gestational age of their first delivery and 70% delivered within 2 weeks. Among 15,863 nulliparous women with singleton births at their first delivery, a history of preterm birth in that pregnancy could predict only 10% of the preterm births that ultimately occurred in the entire obstetric population.
  
  
  CONCLUSIONS
  In a population-based study at our hospital, women who initially delivered preterm and thus were identified to be at risk for recurrence ultimately accounted for only 10% of the prematurity problem in the cohort.
authors.affiliation: Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9032, USA. steven.bloom@utsouthwestern.edu
authors.forename: S L
authors.initials: SL
authors.lastname: Bloom
authors.forename: N P
authors.initials: NP
authors.lastname: Yost
authors.forename: D D
authors.initials: DD
authors.lastname: McIntire
authors.forename: K J
authors.initials: KJ
authors.lastname: Leveno
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007752:Obstetric Labor, Premature / Q000453:epidemiology*; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D011272:Pregnancy, Multiple; D012008:Recurrence; D018570:Risk Assessment