title: Pregnancy and perinatal outcomes in women with polycystic ovary syndrome and twin births: a population-based cohort study.
abstract: OBJECTIVE
  To investigate pregnancy and perinatal outcomes in twin births among women with and without polycystic ovary syndrome (PCOS) diagnosis.
  
  
  METHODS
  Population-based cohort study.
  
  
  METHODS
  Sweden.
  
  
  METHODS
  We identified 20,965 women with twin births between 1995 and 2009 of whom 226 had a PCOS diagnosis through linkage between the Swedish Medical Birth Register and the Swedish National Patient Register.
  
  
  METHODS
  Calculating risk ratios (RR) with 95% confidence intervals (CI) using a log-binomial regression model and hazard ratios (HR) with 95% CI for preterm birth.
  
  
  METHODS
  Preterm birth, low birthweight, caesarean section, pre-eclampsia, Apgar score <7 at 5 minutes and perinatal mortality.
  
  
  RESULTS
  PCOS diagnosis in twin pregnancy was associated with increased risk of preterm delivery (51% versus 43%, RR 1.18 [95% CI 1.03-1.37]), particularly spontaneous preterm delivery (37% versus 28%; RR 1.30 [95% CI 1.09-1.55]) and very preterm birth (<32 weeks) (14% versus 8%, RR 1.62 [95% CI 1.10-2.37]). Twins of PCOS mothers had more often low birthweight (48% versus 39%, adjusted RR 1.40 [95% CI 1.09-1.80]). This difference disappeared when adjusting for gestational age. No risk difference was found for caesarean section, pre-eclampsia, low 5-minute Apgar score or perinatal mortality.
  
  
  CONCLUSIONS
  The risk of preterm delivery in twin pregnancies is increased by having a PCOS diagnosis. This should be considered in risk estimation and antenatal follow-up of twin pregnancies.
authors.affiliation: Institute of Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway.|Department of Obstetrics and Gynaecology, St Olavs Hospital, Trondheim, Norway.
authors.forename: T S
authors.initials: TS
authors.lastname: Løvvik
authors.affiliation: Department of Medicine, Solna, Clinical Epidemiology Unit, Karolinska Institute, Stockholm, Sweden.|Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden.
authors.forename: A-K
authors.initials: AK
authors.lastname: Wikström
authors.affiliation: Department of Medicine, Solna, Clinical Epidemiology Unit, Karolinska Institute, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Neovius
authors.affiliation: Department of Medicine, Solna, Clinical Epidemiology Unit, Karolinska Institute, Stockholm, Sweden.|Division of Obstetrics and Gynaecology, Department of Women's and Children's Health, Karolinska Institute, Stockholm, Sweden.
authors.forename: O
authors.initials: O
authors.lastname: Stephansson
authors.affiliation: Department of Medicine, Solna, Clinical Epidemiology Unit, Karolinska Institute, Stockholm, Sweden.|Division of Obstetrics and Gynaecology, Department of Women's and Children's Health, Karolinska Institute, Stockholm, Sweden.
authors.forename: N
authors.initials: N
authors.lastname: Roos
authors.affiliation: Institute of Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway.|Department of Obstetrics and Gynaecology, St Olavs Hospital, Trondheim, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Vanky
mesh_terms: D000293:Adolescent; D000328:Adult; D001034:Apgar Score; D002585:Cesarean Section / Q000706:statistics & numerical data; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D016017:Odds Ratio; D054238:Perinatal Mortality; D011085:Polycystic Ovary Syndrome; D011225:Pre-Eclampsia / Q000209:etiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000209:etiology*; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin; D047928:Premature Birth / Q000209:etiology; D012042:Registries; D012044:Regression Analysis; D055815:Young Adult
keywords: Cohort study; polycystic ovary syndrome; pregnancy outcome; preterm birth; twins