Prospective evaluation of luteal phase length and natural fertility

Abstract

Objective: To evaluate the impact of a short luteal phase on fecundity.

Design: Prospective time-to-pregnancy cohort study.

Setting: Not applicable.

Patient(s): Women trying to conceive, ages 30-44 years, without known infertility.

Intervention(s): Daily diaries, ovulation prediction testing, standardized pregnancy testing.

Main outcome measure(s): Subsequent cycle fecundity.

Result(s): Included in the analysis were 1,635 cycles from 284 women. A short luteal phase (≤11 days including the day of ovulation) occurred in 18% of observed cycles. Mean luteal phase length was 14 days. Significantly more women with a short luteal phase were smokers. After adjustment for age, women with a short luteal phase had 0.82 times the odds of pregnancy in the subsequent cycle immediately following the short luteal phase compared with women without a short luteal phase. Women with a short luteal length in the first observed cycle had significantly lower fertility after the first 6 months of pregnancy attempt, but at 12 months there was no significant difference in cumulative probability of pregnancy.

Conclusion(s): Although an isolated cycle with a short luteal phase may negatively affect short-term fertility, incidence of infertility at 12 months was not significantly higher among these women.

Clinical trial registration number: NCT01028365.

Keywords: Short luteal phase; fecundity; luteal phase deficiency; natural fertility.