title: Outcomes in twin pregnancies reduced to singleton pregnancies compared with ongoing twin pregnancies.
abstract: OBJECTIVE
  Multifetal pregnancy reduction has been shown to improve outcomes in triplet and higher-order multiple pregnancies. The data for fetal reduction of twin pregnancies are limited. The purpose of this study was to compare adverse pregnancy outcomes in ongoing twin pregnancies compared with twin pregnancies reduced to singletons.
  
  
  METHODS
  This was a retrospective cohort study comparing dichorionic diamniotic twin pregnancies with dichorionic diamniotic twin pregnancies reduced to singleton gestations between 11 and 24 weeks' gestation in a single maternal-fetal medicine practice over a 9 year period. Adverse pregnancy outcomes after 24 weeks were compared, with a value of P < .05 used for significance.
  
  
  RESULTS
  Five hundred one ongoing twin pregnancies and 63 twin pregnancies reduced to singletons were included. Patients with reductions to singletons had a significantly lower risk of preterm delivery before 37 weeks' gestation (10% vs 43%; P < .001) but no difference in the risk of preterm delivery before 34 weeks' or 28 weeks' gestation. Patients with reductions to singletons also had a lower risk of infant birthweight less than the 10% (23% vs 49%; P < .001) but no difference in the risk of infant birthweight less than the 5%. There was no difference in the risk of fetal demise after 24 weeks' gestation.
  
  
  CONCLUSIONS
  Fetal reduction of twin pregnancies decreases the risk of late preterm birth and birthweight less than the 10% but not the risks of more severe complications such as early preterm birth or birthweight less than the 5%.
authors.affiliation: Maternal-Fetal Medicine Associates, PLLC, New York, NY; Department of Obstetrics, Gynecology, and Reproductive Science, Icahn School of Medicine at Mount Sinai, New York, NY. Electronic address: simikgupta@gmail.com.
authors.forename: Simi
authors.initials: S
authors.lastname: Gupta
authors.affiliation: Maternal-Fetal Medicine Associates, PLLC, New York, NY; Department of Obstetrics, Gynecology, and Reproductive Science, Icahn School of Medicine at Mount Sinai, New York, NY.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Fox
authors.affiliation: Maternal-Fetal Medicine Associates, PLLC, New York, NY.
authors.forename: Jessica
authors.initials: J
authors.lastname: Feinberg
authors.affiliation: Maternal-Fetal Medicine Associates, PLLC, New York, NY; Department of Obstetrics, Gynecology, and Reproductive Science, Icahn School of Medicine at Mount Sinai, New York, NY.
authors.forename: Chad K
authors.initials: CK
authors.lastname: Klauser
authors.affiliation: Maternal-Fetal Medicine Associates, PLLC, New York, NY; Department of Obstetrics, Gynecology, and Reproductive Science, Icahn School of Medicine at Mount Sinai, New York, NY.
authors.forename: Andrei
authors.initials: A
authors.lastname: Rebarber
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D005313:Fetal Death; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D011247:Pregnancy; D011256:Pregnancy Outcome; D018607:Pregnancy Reduction, Multifetal / Q000706:statistics & numerical data*; D059285:Pregnancy, Twin; D047928:Premature Birth / Q000453:epidemiology*; D012189:Retrospective Studies
keywords: multifetal pregnancy reduction; selective reduction; twin pregnancy