Longer time to pregnancy with irregular sleeping patterns

A 2025 study found that in women trying to conceive without fertility issues, those with regular sleep patterns became pregnant more quickly.

Poor or irregular sleep is linked to a variety of health problems, including increased risk of some chronic diseases and reproductive issues like reduced fertility and preterm birth. A problem with many of these studies is that they rely on self-reported sleep data, which can be inaccurate.

This post is a summary of a study by Zhao et al. (2025) who measured sleep patterns in women trying to conceive and reported on their time to pregnancy over the course of a year.

To measure sleep patterns, participants wore a special kind of watch called an actigraphy watch for two weeks and were contacted monthly to report any pregnancies. Using the watch, the researchers measured:

• Sleep onset: The time when you begin sleeping.
• Sleep offset: The time when you wake up and end your sleep period.
• Sleep midpoint: The time exactly halfway between when you fall asleep and when you wake up.
• Sleep duration: The total amount of time you spend sleeping, from sleep onset to sleep offset.
• Day-to-day variability: The amount of change or inconsistency in your sleep times from one day to the next, measured by the standard deviation of these differences.

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Study details

• This was a secondary analysis of a prospective pilot study conducted in the US between 2015 and 2017. The original study was from Zhao et al. (2022).
• Women aged 18–45 with regular periods who were trying to get pregnant were included.
• Infertility patients were excluded.

In terms of sample size, there were 252 women in the study, with 69 being excluded because they didn’t have useable actigraphy watch data. In the end, there were 183 participants.

In terms of baseline characteristics, participants showed differences in BMI, race, education, income and cigarette smoking. These confounders, along with maternal age, were statistically adjusted in their hazard ratio calculations.

Irregular sleep onset, duration affect time to pregnancy

For sleep onset, participants went to bed at an average time of 10:55 PM, with 109 minutes of variability on average.

• Women with irregular bedtimes (varying by more than 1.8 hours day-to-day) had a longer time to pregnancy compared to regular sleepers (adjusted hazard ratio [95% CI]: 0.60 [0.36–0.999]).
• For the top 25% of women with the most irregular bedtimes, they had an even longer time to become pregnant compared to the most regular sleepers (adjusted hazard ratio [95% CI]: 0.33 [0.15-0.74]).
• There was no difference in time to pregnancy for participants who went to bed early or late.

For sleep offset, participants typically woke up around 7:23 AM, with 102 minutes of variability.

• There were no differences in time to pregnancy for participants based on their sleep offset.

For sleep midpoint, the time between sleep onset and offset averaged to 3:08 AM, with 82 minutes of variability.

• There were no differences in time to pregnancy for participants based on their sleep midpoints.

For sleep duration, the average length of sleep was 508 minutes (roughly 8.5 hours), with 139 minutes of variability.

• Women with greater variability in sleep duration (varying by more than 2.3 hours day-to-day) had a longer time to pregnancy (adjusted hazard ratio [95% CI]: 0.59 [0.36-0.98]).
• There was no difference in time to pregnancy for participants who had a short vs long sleep duration.

Conclusions

This study found that participants who had variable sleeping patterns, like irregular bedtimes and sleep duration, took longer to become pregnancy. There were no differences in early/late bedtimes, the time the participants woke up, the duration of sleep itself, or the midpoint from when they went to bed and woke up.

So based on this, it looks like having a consistent bedtime and length of sleep is important for reducing time to pregnancy, which suggests improved fertility for these participants.

The authors explain that sleep disruption can affect fertility by causing misalignment of circadian rhythms, which can alter reproductive hormones like melatonin, LH and FSH. It’s possible that this could impair processes like ovulation and egg development.

Although the participants were attempting pregnancy, they didn’t record the number of conception attempts and it’s possible that some participants didn’t have sex as frequently. This was mentioned as a limitation. It’s also possible that people who have a consistent bedtime/duration of sleep might have a more healthy lifestyle, which could contribute to fertility. I’ll also highlight that this study was NOT done in infertile patients, so it’s not clear if these results would hold true for infertility patients.

The authors note that this was a small study, and larger research is needed to confirm the findings and determine if regular sleep schedules can help women trying to conceive.

For more reading on the topic that relates more to IVF, check out my post Sleep quality and its impact on IVF outcomes. It goes over a study where researchers compared sleep characteristics for women of different ages, and found that women who slept 7-9 hours a night, and had good quality sleep, had optimal IVF outcomes.

Reference

Zhao P, Jungheim ES, Bedrick BS, Wan L, Jimenez PT, McCarthy R, Chubiz J, Fay JC, Herzog ED, Sutcliffe S, England SK. Sleep variability and time to achieving pregnancy: findings from a pilot cohort study of women desiring pregnancy. Fertil Steril. 2025 Jan 24:S0015-0282(25)00046-9. doi: 10.1016/j.fertnstert.2025.01.019. Epub ahead of print. PMID: 39864791.

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About Embryoman

Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.

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