title: Relative contributions of anovulation and luteal phase defect to the reduced pregnancy rate of breastfeeding women.
abstract: OBJECTIVE
  To evaluate the contribution of anovulation and luteal phase defects to lactational infertility.
  
  
  METHODS
  Prospective longitudinal follow-up.
  
  
  METHODS
  Outpatient clinic.
  
  
  METHODS
  Forty-nine women fully nursing and amenorrheic on day 75 postpartum and 25 cycling, interval non-nursing women.
  
  
  METHODS
  Plasma prolactin, luteinizing hormone, estradiol (E2), and progesterone (P) levels twice a week up to the second postpartum menses.
  
  
  METHODS
  Ovulation rate and endocrine profile of the menstrual cycles.
  
  
  RESULTS
  Ovulation rates were 37% and 97% at 6 and 12 months postpartum; 67% of ovulations occurred in amenorrhea. The luteal phase was shorter, and E2 and P levels were lower in lactating women than in non-nursing women. These parameters were closer to normal in the second cycle than the first, in spite of active nursing. The risk of ovulation and pregnancy in amenorrhea was 27.7% and 0.9% at month 6 postpartum. After the first menses, these risks were 93% and 7%, respectively.
  
  
  CONCLUSIONS
  The abnormal endocrine profile of the first luteal phase offers effective protection to women who ovulate during lactational amenorrhea within the first 6 months after delivery. Later luteal phases are improved and women are at risk of pregnancy.
authors.affiliation: Pontificia Universidad Católica de Chile, Santiago.
authors.forename: S
authors.initials: S
authors.lastname: Díaz
authors.forename: H
authors.initials: H
authors.lastname: Cárdenas
authors.forename: A
authors.initials: A
authors.lastname: Brandeis
authors.forename: P
authors.initials: P
authors.lastname: Miranda
authors.forename: A M
authors.initials: AM
authors.lastname: Salvatierra
authors.forename: H B
authors.initials: HB
authors.lastname: Croxatto
mesh_terms: D000293:Adolescent; D000328:Adult; D000858:Anovulation; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D007774:Lactation / Q000502:physiology*; D008137:Longitudinal Studies; D008183:Luteal Phase / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D011388:Prolactin / Q000097:blood; D011446:Prospective Studies
chemical_list: D011374:Progesterone; D004958:Estradiol; D011388:Prolactin; D007986:Luteinizing Hormone