Prospective evaluation of the impact of intermenstrual bleeding on natural fertility

An episode of intermenstrual bleeding statistically significantly decreases the odds of conception in the current cycle but does not appear to negatively impact a woman’s future reproductive potential.


Natalie M. Crawford, M.D., David A. Pritchard, M.S., Amy H. Herring, Sc.D., Anne Z. Steiner, M.D., M.P.H.

Volume 105, Issue 5, Pages 1294-1300



To evaluate the impact of an episode of intermenstrual bleeding on the probability of conception in a menstrual cycle (fecundability).


Prospective, time-to-pregnancy cohort study.


Community-based cohort.


Women trying to conceive, ages 30 to 44 years, without known infertility.


Not applicable.

Main Outcome Measure(s):

Current cycle and subsequent cycle fecundability.


A total of 549 women provided 1,552 complete cycles for analysis. Intermenstrual and luteal bleeding were reported in 36% and 34% of cycles, respectively. Ninety-three percent of all intermenstrual bleeding was luteal. Cycles in which women had intermenstrual bleeding or luteal bleeding were statistically significantly less likely to result in conception (fecundability ratio [FR] 0.23; 95% confidence interval [CI], 0.16–0.34; and FR 0.22; 95% CI, 0.14–0.33). Women with an episode of intermenstrual and luteal bleeding had a statistically significant increase in the probability of pregnancy in the subsequent cycle (FR 1.61; 95% CI, 1.15–2.25; and FR 2.01; 95% CI, 1.52–2.87, respectively).


Intermenstrual bleeding statistically significantly decreases the odds of conceiving in that cycle but does not appear to negatively impact a woman’s immediate future reproductive potential.

Clinical Trial Registration Number:


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