title: Risk of adverse pregnancy outcomes by prepregnancy body mass index: a population-based study to inform prepregnancy weight loss counseling.
abstract: OBJECTIVE
  To estimate the absolute risks of adverse maternal and perinatal outcomes based on small differences in prepregnancy body mass (eg, 10% of body mass or 10-20 pounds).
  
  
  METHODS
  This population-based cohort study (N=226,958) was drawn from all singleton pregnancies in British Columbia (Canada) from 2004 to 2012. The relationships between prepregnancy body mass index (BMI) (as a continuous, nonlinear variable) and adverse pregnancy outcomes were examined using logistic regression models. Analyses were adjusted for maternal age, height, parity, and smoking in pregnancy. Adjusted absolute risks of each outcome are reported according to incremental differences in prepregnancy BMI and weight in pounds.
  
  
  RESULTS
  A 10% difference in prepregnancy BMI was associated with at least a 10% lower risk of preeclampsia, gestational diabetes, indicated preterm delivery, macrosomia, and stillbirth. In contrast, larger differences in prepregnancy BMI (20-30% differences in BMI) were necessary to meaningfully reduce risks of cesarean delivery, shoulder dystocia, neonatal intensive care unit stay 48 hours or longer, and in-hospital newborn mortality. Prepregnancy BMI was not associated with risk of postpartum hemorrhage requiring intervention, severe maternal morbidity or maternal mortality, or spontaneous preterm delivery before 32 weeks of gestation.
  
  
  CONCLUSIONS
  These results can inform prepregnancy weight loss counseling by defining achievable weight loss goals for patients that may reduce their risk of poor perinatal outcomes.
  
  
  METHODS
  II.
authors.affiliation: Departments of Epidemiology and Social and Behavioral Sciences, Harvard School of Public Health, and the Departments of Pediatric Newborn Medicine and Obstetrics and Gynecology, Brigham and Women's Hospital, Boston, Massachusetts; the Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver, British Columbia, Canada; and Magee-Women's Research Institute, Departments of Obstetrics, Gynecology, and Reproductive Sciences and Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania.
authors.forename: Laura
authors.initials: L
authors.lastname: Schummers
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Hutcheon
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Bodnar
authors.forename: Ellice
authors.initials: E
authors.lastname: Lieberman
authors.forename: Katherine P
authors.initials: KP
authors.lastname: Himes
mesh_terms: D000328:Adult; D015992:Body Mass Index; D001955:British Columbia / Q000453:epidemiology; D002585:Cesarean Section / Q000706:statistics & numerical data; D015331:Cohort Studies; D037001:Directive Counseling; D005260:Female; D005320:Fetal Macrosomia / Q000453:epidemiology; D006801:Humans; D009765:Obesity / Q000453:epidemiology*; D011225:Pre-Eclampsia / Q000453:epidemiology; D016742:Preconception Care; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D047928:Premature Birth / Q000453:epidemiology; D018570:Risk Assessment; D050497:Stillbirth / Q000453:epidemiology; D015431:Weight Loss; D055815:Young Adult