title: Maternal obesity in singleton versus twin gestations: a population-based matched case-control study.
abstract: OBJECTIVE
  To examine the impact of pre-pregnancy obesity on adverse outcomes in twin compared to singleton pregnancies.
  
  
  METHODS
  Dichorionic twin gestations with maternal body mass index >30 were matched to three singleton controls. Both obese groups were matched (1:3) with non-obese controls. Rates of preeclampsia, gestational diabetes, cesarean section, and preterm birth were compared.
  
  
  RESULTS
  One hundred eighty-nine dichorionic twin pregnancies in obese mothers were matched to 567 twin pregnancies in non-obese mothers, and to 567 singleton pregnancies in obese mothers. The latter were matched to 1701 non-obese mothers with singletons. Preeclampsia was more common in obese mothers with both twins and singletons (odds ratio (OR) 3.95, 95% confidence interval (CI) 2.18-7.16 and OR 6.53, 95% CI 3.75-11.4, respectively) as was gestational diabetes (OR 4.35, 95% CI 2.18-8.69; OR 5.53 95% CI 3.60-8.50). Obese mothers with singletons were more likely to deliver abdominally, but the cesarean rates were obesity independent in twins. Obese mothers were more likely to deliver at < 34 weeks in both twin and singleton groups (OR 1.65, 95% CI 1.10-2.48, and OR 2.41, 95% CI 1.21-4.77, respectively).
  
  
  CONCLUSIONS
  Obesity-attributable adverse outcomes are lower in twins compared to singletons. Obesity increases the risk of preterm birth regardless of plurality.
authors.affiliation: Department of Perinatology, Division of Obstetrics and Gynecology, University Medical Centre Ljubljana , Ljubljana , Slovenia and.
authors.forename: Miha
authors.initials: M
authors.lastname: Lucovnik
authors.forename: Isaac
authors.initials: I
authors.lastname: Blickstein
authors.forename: Ivan
authors.initials: I
authors.lastname: Verdenik
authors.forename: Andreja
authors.initials: A
authors.lastname: Trojner-Bregar
authors.forename: Natasa
authors.initials: N
authors.lastname: Tul
mesh_terms: D015992:Body Mass Index; D016022:Case-Control Studies; D002585:Cesarean Section / Q000706:statistics & numerical data; D016640:Diabetes, Gestational / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D009035:Mothers / Q000706:statistics & numerical data; D009765:Obesity / Q000453:epidemiology*; D010298:Parity; D011225:Pre-Eclampsia / Q000453:epidemiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D011256:Pregnancy Outcome / Q000453:epidemiology*; D059285:Pregnancy, Twin / Q000706:statistics & numerical data*
keywords: Body mass index; gestational diabetes mellitus; preeclampsia; pregnancy; preterm birth; twins