title: The Preterm Prediction Study: association of cesarean delivery with increases in maternal weight and body mass index.
abstract: OBJECTIVE
  Our purpose was to evaluate whether maternal weight and body mass index measured either before or during pregnancy are associated with an increased risk of cesarean delivery.
  
  
  METHODS
  Maternal weight and height were prospectively collected on 2929 women in the National Institutes of Health Maternal-Fetal Medicine Units Network Preterm Prediction Study. Prepregnancy and 27- to 31-week maternal weight and height were used to calculate the body mass index, and its contribution to the risk of cesarean delivery was determined. Women with prenatally diagnosed congenital anomalies (n = 89) and pregestational diabetes (n = 31) were excluded from analysis.
  
  
  RESULTS
  Univariate analysis of risk factors for cesarean delivery in the 2809 eligible women revealed a decreased risk of cesarean delivery with maternal age < 18 years and multiparity; increased risk of cesarean delivery was noted with maternal age > 35 years and a male fetus. Increases in either prepregnancy or 27- to 31-week maternal weight (5-pound units) or body mass index (1.0 kg/m2 units) were significantly associated with an increased odds of cesarean delivery (p = 0.0001). Each unit increase in prepregnancy or 27- to 31-week body mass index resulted in a parallel increase in the odds of cesarean delivery of 7.0% and 7.8%, respectively. Multivariable stepwise logistic regression analysis confirmed the association of male fetus, age, nulliparity, and body mass index as significant variables contributing to cesarean delivery risk.
  
  
  CONCLUSIONS
  The risk of cesarean delivery is associated with incremental changes in maternal weight and body mass index before and during pregnancy after adjustment for potential confounding factors. Prepregnancy counseling about optimizing maternal weight and monitoring weight gain during pregnancy to decrease the risk of cesarean delivery are supported by this study.
authors.affiliation: Maternal-Fetal Medicine Units Network, National Institute of Child Health and Human Development, Bethesda, Maryland, USA.
authors.forename: B C
authors.initials: BC
authors.lastname: Brost
authors.forename: R L
authors.initials: RL
authors.lastname: Goldenberg
authors.forename: B M
authors.initials: BM
authors.lastname: Mercer
authors.forename: J D
authors.initials: JD
authors.lastname: Iams
authors.forename: P J
authors.initials: PJ
authors.lastname: Meis
authors.forename: A H
authors.initials: AH
authors.lastname: Moawad
authors.forename: R B
authors.initials: RB
authors.lastname: Newman
authors.forename: M
authors.initials: M
authors.lastname: Miodovnik
authors.forename: S N
authors.initials: SN
authors.lastname: Caritis
authors.forename: G R
authors.initials: GR
authors.lastname: Thurnau
authors.forename: S F
authors.initials: SF
authors.lastname: Bottoms
authors.forename: A
authors.initials: A
authors.lastname: Das
authors.forename: D
authors.initials: D
authors.lastname: McNellis
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D002585:Cesarean Section; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008423:Maternal Age; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D011446:Prospective Studies; D012307:Risk Factors; D012737:Sex Factors