Sporadic Anovulation is Not an Important Determinant of Becoming Pregnant and Time to Pregnancy Among Eumenorrheic Women: A Simulation Study

Background: Attaining pregnancy is conditional upon a series of complex processes, including adequately timed intercourse, ovulation, fertilisation, and implantation. Anovulation is a first-line treatment target for couples with difficulty conceiving and is frequently examined in studies of fecundability.

Objectives: To identify whether sporadic anovulation is an important determinant of cumulative pregnancy rates and time to pregnancy among fertile women with regular menstrual cycles.

Methods: We simulated cumulative pregnancy rates and time to pregnancy for 12 consecutive menstrual cycles among 100 000 women based on data-driven probabilities of implantation, fertilisation, ovulation, and intercourse occurring in the fertile window. We assumed anovulation probabilities of 1%, 8%, or 14.5% and intercourse averaging once per week, every other day, or daily. The model incorporated reductions in implantation and fertilisation rates for successive cycles of non-pregnancy.

Results: After 12 cycles, a reduction in the per cycle incidence of anovulation from 14.5% to 1% resulted in a 4.0% higher cumulative pregnancy rate (86.7% vs 90.7%) and similar time to pregnancy (1-cycle median difference). In contrast, increasing mean unscheduled sexual intercourse frequency from weekly to every other day was associated with a 5-cycle median reduction in time to pregnancy (weekly: 7 cycles; every other day or daily: 2 cycles) and a 28.9% increase in the cumulative pregnancy rate (weekly: 59.9%, every other day: 88.8%; daily: 91.6%).

Conclusions: In presumed fertile women with regular menstrual cycles, routine investigation of anovulation may not be an informative outcome in studies of fecundability, and routine testing to ensure ovulation and treatment of anovulation are unlikely to be medically necessary. While biomarkers or cervical fluid may help time intercourse to the fertile window, time to pregnancy can also be improved through increasing the frequency of unscheduled intercourse. These findings need corroboration in large preconception time to pregnancy studies.