Relative contributions of anovulation and luteal phase defect to the reduced pregnancy rate of breastfeeding women

Fertil Steril. 1992 Sep;58(3):498-503.


Objective: To evaluate the contribution of anovulation and luteal phase defects to lactational infertility.

Design: Prospective longitudinal follow-up.

Setting: Outpatient clinic.

Subjects: Forty-nine women fully nursing and amenorrheic on day 75 postpartum and 25 cycling, interval non-nursing women.

Interventions: Plasma prolactin, luteinizing hormone, estradiol (E2), and progesterone (P) levels twice a week up to the second postpartum menses.

Main outcome measures: 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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Anovulation*
  • Estradiol / blood
  • Female
  • Humans
  • Lactation / physiology*
  • Longitudinal Studies
  • Luteal Phase / physiology*
  • Luteinizing Hormone / blood
  • Pregnancy
  • Progesterone / blood
  • Prolactin / blood
  • Prospective Studies


  • Progesterone
  • Estradiol
  • Prolactin
  • Luteinizing Hormone