title: Characteristics and determinants of postpartum ovarian function in women in the United States.
abstract: OBJECTIVE
  Our aim was to characterize the influence of breast-feeding on the postpartum return of ovarian activity for the purpose of assessing the relevance of the lactational amenorrhea method of contraception for women in the United States.
  
  
  METHODS
  Twenty-two non-breast-feeding and 60 breast-feeding women from Baltimore collected daily urine specimens that were assayed to determine ovulation and luteal phase adequacy. Vaginal bleeding was ascertained weekly, and breast-feeding women recorded infant feeding daily. Proportion-hazards models were used to relate measures of breast-feeding to the occurrence of ovulation.
  
  
  RESULTS
  Two thirds of women ovulated before their first vaginal bleeding, but 47% of those cycles had decreased luteal-phase pregnanediol excretion. Breast-feeding frequency and suckling duration were significant predictors of the risk of ovulation (p < 0.001). Supplementation with bottle feeding was associated with a reduction in breast-feeding.
  
  
  CONCLUSIONS
  A high degree of protection from pregnancy can be achieved using breast-feeding frequency and suckling duration, even with supplemented breast-feeding.
authors.affiliation: Department of Population Dynamics, Johns Hopkins School of Hygiene and Public Health.
authors.forename: O M
authors.initials: OM
authors.lastname: Campbell
authors.forename: R H
authors.initials: RH
authors.lastname: Gray
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007774:Lactation / Q000502:physiology*; D008183:Luteal Phase / Q000502:physiology; D008598:Menstruation; D010053:Ovary / Q000502:physiology*; D010060:Ovulation; D049590:Postpartum Period / Q000502:physiology*; D014481:United States