BackgroundFertility success among mixed-sex couples often depends on frequency and timing of sexual intercourse, yet little research has evaluated the association between preconception sexual function and time-to-pregnancy (TTP). Objective(s): To evaluate the effects of female sexual dysfunction, distress related to sexual functioning, and painful intercourse on TTP. Study DesignWe followed 2,500 participants from Pregnancy Study Online (PRESTO), a prospective cohort study of self-identified females attempting pregnancy without the use of fertility treatments. Participants enrolled between 2021 and 2024. Thirty days after enrollment, participants completed a supplemental questionnaire that contained questions about sexual health, including a modified version of the 6-item Female Sexual Function Index (score range 2-30, score ≤19 defined as sexual dysfunction) and the Female Sexual Distress Scale (score range 0-48, score ≥20 defined as clinically-relevant distress), which assess experiences in the previous 4 weeks. Participants completed the supplemental questionnaire no later than 6 months after initiating conception attempts. We estimated TTP based on self-reported pregnancy status on follow-up questionnaires completed every 8 weeks for up to 12 months. We used proportional probabilities regression to calculate fecundability ratios (FRs) and 95% confidence intervals (CIs) relating exposure measures with TTP, adjusting for a range of pre-specified confounders. As an exploratory analysis, we evaluated individual domains of sexual function (i.e., interest, arousal, orgasm, lubrication, and satisfaction) in relation to TTP. ResultsThe study population was primarily non-Hispanic White, high income, with college or graduate education. Exposure prevalence was 20.1% for female sexual dysfunction, 8.8% for distress, and 29.6% for any pain with intercourse. We observed no association between FSD and TTP (adjusted FR 1.00, 95% CI 0.890, 1.13) when FSD was defined using a clinically-validated cut point, but observed that those in the first, second, and third quartile of scores had delayed conception compared to those in the fourth (highest function) (adjusted FRs 0.90, 95% CI 0.76, 1.06; 0.88, 95% CI 0.75, 1.04; and 0.90, 95% CI 0.77, 1.04, respectively). We found 18% reduced fecundability among those with sexual distress as defined by a clinically-validated cut point compared to those without (adjusted FR 0.82, 95% CI 0.69, 0.98). Participants reporting painful intercourse most or all the time had a longer TTP than those reporting no pain (adjusted FR 0.81, 95% CI 0.62, 1.06). In exploratory analyses, lower function in orgasm and lubrication domains, but not interest, desire, and arousal, were associated with longer TTP. Conclusion(s)Preconception sexual dysfunction, specifically distress and frequent painful intercourse, was associated with delayed conception. Preconception clinical assessment of sexual function, including discussion of individual domains of sexual function, may elucidate important modifiable issues.