title: Method of delivery and neonatal mortality among very low birth weight infants in the United States.
abstract: OBJECTIVE
  To examine the association between method of delivery (primary cesarean section vs. vaginal) and neonatal mortality risk (as well as causes of death) among very low-birth weight first-born infants in the United States. More specifically, to examine this association separately for breech/malpresenting and vertex-presenting infants, while adjusting for selected maternal characteristics, and pregnancy, labor and delivery complications.
  
  
  METHODS
  The study population was derived from the 1995-1998 birth cohort linked birth/infant death data sets. Binary and multinomial logit regression analyses were performed to assess the relationship in four very low-birth weight categories.
  
  
  RESULTS
  Among breech/malpresenting neonates, compared to those delivered vaginally, infants delivered by a primary cesarean section had significantly lower adjusted relative risks of death for all very low-birth weight categories and the decrease in relative risk tended to be larger with each increasing birth weight category. However, for vertex-presenting neonates, results are mixed, suggesting decreased relative mortality risks associated with primary cesarean section, which were significant for 500-749 g, not significant for 750-999 g, and barely significant for 1,000-1,249 g. In contrast, for vertex-presenting neonates weighing 1,250-1,499 g, there was a significantly increased adjusted relative risk associated with primary cesarean section. Differences in cause-specific neonatal mortality by method of delivery and presentation status were also discussed.
  
  
  CONCLUSIONS
  Primary cesarean section appears to be associated with decreased neonatal mortality risks in each very low-birth weight category for breech/malpresenting infants, but results are mixed for vertex-presenting infants. Causal inferences should be avoided because this was an observational study by design.
authors.affiliation: Office of Applied Studies, Substance Abuse and Mental Health Services Administration (SAMHSA), Rockville, MD 20857, USA. pradip.muhuri@samhsa.hhs.gov
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Muhuri
authors.forename: Marian F
authors.initials: MF
authors.lastname: Macdorman
authors.forename: Fay
authors.initials: F
authors.lastname: Menacker
mesh_terms: D000328:Adult; D001946:Breech Presentation / Q000453:epidemiology / Q000401:mortality; D002423:Cause of Death; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000379:methods*; D005260:Female; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D019370:Observation; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology / Q000401:mortality*; D012306:Risk; D018570:Risk Assessment; D016019:Survival Analysis; D014481:United States / Q000453:epidemiology; D014710:Version, Fetal / Q000401:mortality / Q000706:statistics & numerical data