title: Maternal pre-gravid body mass index and obstetric outcomes in twin gestations.
abstract: OBJECTIVE
  The aim of this study is to evaluate the impact of maternal pre-gravid and/or first trimester overweight and obesity, and the adverse obstetrics outcome in twin pregnancies.
  
  
  METHODS
  This is a retrospective study of women who delivered viable twins after 23 weeks of gestation with available prepregnancy body mass index (BMI) and/or were at their earliest visit during the first trimester of pregnancy in the period 2007-2011. The patients were divided into four subgroups according to their BMI (underweight, normal weight, overweight and obese) according to the WHO classification and their outcomes were compared. Obstetrical outcomes of interest including gestational diabetes, gestational hypertension, preterm birth, antepartum hemorrhage, intrahepatic cholestasis of pregnancy, method of delivery and neonatal intensive care unit (NICU) admission were all studied and compared.
  
  
  RESULTS
  Electronic records of 1228 pregnant subjects who delivered twins were abstracted. Five hundred and four patients with twin gestations with available BMI were identified (underweight BMI<18.5% (n=22), normal weight BMI 18.5-24.9% (n=260), overweight 25-29.9% (n=114) and obese ⩾30% (n=108)). Obstetric complications occurred more often in the overweight and obese groups as compared with the normal weight group. There was an increased risk of gestational diabetes in overweight and obese women (odds ratio (OR), 3.3; 95% confidence interval (CI) 1.52-7.3; P=0.001) and (OR, 3.2; 95% CI, 1.41-7.1; P=0.002), respectively. There was an increased risk of gestational hypertension in the obese group compared with the normal weight group (OR, 2.29; 95% CI, 1.1-4.7; P=0.02) but not in the overweight group (OR, 1.71; 95% CI, 0.8-3.6; P=0.1). In addition, an increased risk of very preterm delivery (<32 weeks) in the overweight group and obese groups was seen when compared with the normal weight group (OR, 2.2; 95% CI, 1.18-4.20; P=0.014 and OR, 2; 95% CI, 1.024-3.91; P=0.04, respectively). Increased rate of cesarean section in the obese group was seen when compared with the normal weight group (OR, 2; 95% CI, 1.2-3.4; P=0.006). Risks of antepartum hemorrhage, intrahepatic cholestasis and NICU admission were similar between the groups.
  
  
  CONCLUSIONS
  In addition to the known obstetrics complications associated with twin gestations, the pregnancy outcomes in twins are further adversely influenced by increased maternal prepregnancy BMI.
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Al-Obaidly
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Parrish
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: K E
authors.initials: KE
authors.lastname: Murphy
authors.affiliation: Department of Obstetrics and Gynecology, Division of Maternal Fetal Medicine, Mount Sinai Hospital, Toronto, ON, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Maxwell
mesh_terms: D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000379:methods; D016640:Diabetes, Gestational / Q000209:etiology; D005260:Female; D005865:Gestational Age; D006801:Humans; D046110:Hypertension, Pregnancy-Induced / Q000209:etiology; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D009765:Obesity / Q000150:complications; D050177:Overweight / Q000150:complications*; D011247:Pregnancy; D011248:Pregnancy Complications; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin / Q000706:statistics & numerical data*; D012189:Retrospective Studies