Differences in ovarian hormones in relation to parity and time since last birth

Capsule:
Among cycling women, parous women have longer follicular phases and lower estradiol metabolite concentrations than nulliparous women. Estradiol, but not progesterone, metabolite concentrations are positively associated with time since last birth.

Authors:
Emily Barrett, Ph.D., Lauren E. Parlett, Ph.D., Gayle C. Windham, Ph.D., Shanna H. Swan, Ph.D.

Volume 101, Issue 6, Pages 1773–1780.e1

Abstract:

Objective:
To examine ovarian function in relation to parity and time since last birth.

Design:
Cross-sectional study.

Setting:
Health-care program in California.

Patient(s):
346 naturally cycling women, aged 18 to 39 years.

Intervention(s):
None.

Main Outcome Measure(s):
Mean follicular urinary estradiol metabolite concentration (E1C) (cycle days −8 to −1), mean luteal progesterone metabolite concentration (PdG) (days 0 to +10), and cycle phase lengths in ovulatory cycles.

Result(s):
After the women had collected daily urine samples for up to eight menstrual cycles, we measured the E1C and PdG using enzyme-linked immunoassay. The cycle phase lengths were calculated from the hormone profiles and daily diaries. Women who had given birth within the previous 3 years had lower E1C than the nulliparous women and women who last given birth >3 years earlier. Among the parous women, E1C was positively associated with the time since last birth. Women who last gave birth >3 years earlier had longer follicular phases than the nulliparous women. There were no associations between parity and PdG or luteal phase length.

Conclusion(s):
Our cross-sectional data suggest that ovarian function differs in nulliparous and parous women and is positively associated with the time since last birth. Longitudinal research is needed to explore within-woman changes in ovarian function prepartum and postpartum.

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