You’re More Likely to Conceive in Warmer Seasons, Mira Study Finds

Ever felt like your libido is higher in the spring or summer? It might be nature’s way of saying that your chances of getting pregnant are high! 

In Mira’s latest study, we found that when compared to average baseline levels, estradiol levels were elevated during the spring and summer months – meaning our chances of conception improve during hotter seasons.  

Read on to see what we’ve learned from our research of 800+ Mira users and how you can use these findings to maximize your hormone health and fertility.  

Setting the Stage: The Relationship Between Seasons, Hormones, and Fertility

You may already be familiar with the body’s circadian rhythm or ‘biological clock’ – i.e. 24-hour cycles that help coordinate key physiological processes like sleep, body temperature, metabolism, and hormones. 

But did you know that some processes also have a distinct circannual rhythm (i.e. yearly cycles) that follow a seasonal pattern?

Hormones in particular have been shown to follow seasonal patterns in both men and women – as demonstrated in this 2020 study of millions of hormone tests. According to the study, follicle-stimulating hormone (FSH) levels in female individuals were elevated during the summer season. This in turn influences estradiol (the active form of estrogen in women of reproductive age), which was found to peak during early spring and summer. 

Interestingly, studies also show that sperm counts are higher during warmer months as well. For example, a study conducted in Sweden found that men’s sperm counts were highest during the spring, with levels increasing by up to 50% compared to the winter months. Another study from the United States found that men’s testosterone levels were highest in the spring, with levels peaking in April.

So what does this mean for fertility? It means that couples have higher chances of conception during warmer months. 

About Mira’s Hormonal-Seasonality Study

At Mira, we wanted to see for ourselves how sex hormone levels shift throughout the year. 

In this hormonal-seasonality study, we investigated hormonal fluctuations among Mira users during the four seasons (summer, spring, fall, and winter). 

Hormones analyzed in this study were:

• Luteinizing hormone (LH)
• Estrone-3-glucuronide (E3G) – the urine metabolite of estradiol
• Pregnanediol glucuronide (PdG) – the urine metabolite of progesterone 

Study participants were selected retrospectively from Mira’s back-end data, from the period January 1, 2022 to December 31, 2022. 

The eligibility criteria for each season included a random selection of 200 women aged 18-45 years with regular menstrual cycle length (21-35 days) who used Mira Max Wands for at least 55% of their cycle. These users were selected from geographical locations of the USA and Canada, as these countries have similar seasonal variations. All users chosen for analysis had selected “healthy” under the app log and they did not have a pregnancy log. 

To analyze the seasonal variation, we grouped Mira users into two groups: hot season (spring and summer) and cold season (fall and winter).

Key Insights

Our analysis includes a total of 804 users (219 Mira users in summer, 200 Mira users in fall, 193 Mira users in spring, and 194 Mira users in winter). 

Here’s what we found:

You’re more likely to get pregnant in the summer

Compared to colder seasons (fall and winter), we found that average E3G levels were elevated during hotter seasons (spring and summer), when compared to the average baseline levels. This was visible during the follicular and luteal phases of users’ menstrual cycle. 

On the other hand, both PdG and LH levels were elevated during colder seasons (fall and winter) when compared to hotter seasons. 

Seasonality of Average Hormone Levels
Spring	Summer	Fall	Winter
E3G – elevatedLH – not elevatedPdG – not elevated	E3G – elevatedLH – not elevatedPdG – not elevated	E3G – not elevatedLH – elevatedPdG – elevated	E3G – not elevatedLH – elevatedPdG – elevated
Overall, we observed lower LH levels, lower PdG levels, and higher E3G levels during hotter seasons (spring and summer) compared to the colder seasons (fall and winter).

We know that research shows estrogen (E3G) is an important indicator of a woman’s ability to conceive. This is because of the role that it plays in helping to create a favorable environment for sperm to reach and fertilize an egg. 

Therefore, elevated estrogen (E3G) levels during hotter seasons suggest that women are more fertile in the spring and summer. This aligns with previous research that shows women, on average, ovulate more frequently during summer – meaning they have an increased chance of conception during the hotter months of the year. 

Your menstrual cycle is likely to be shorter during the spring and summer

We also took a look at the average menstrual cycle length and length of menstruation across each season. 

The length of menstruation (i.e. periods) did not show a difference among Mira users, with the average period lasting 4.8 to 4.9 days. 

However, we did observe that the average menstrual cycle length was noticeably shorter during the spring and summer (27 days) compared to fall and winter (29 days). 

Cycle & Menstrual Days Length
	Spring	Summer	Fall	Winter
Average Length of Menstruation:	4.8- 4.9 days	4.8- 4.9 days	4.8- 4.9 days	4.8- 4.9 days
Average Menstrual Cycle Length:	27 days	27 days	29 days	29 days
The average length of menstruation did not change across seasons. However, the average menstrual cycle length was shorter during the spring and summer compared to the fall and winter.

We also investigated changes in menstrual cycle phase lengths (i.e. the follicular, ovulation, and luteal phase). However, we observed no statistical differences in menstrual cycle phase length across each season. 

Your seasonal hormone patterns may change with age

We also wanted to see if there were any age-related seasonal variations in LH, E3G, and PdG levels. 

To do this, we grouped Mira users into three different age groups: 25-34 years (mid-reproductive age), 35-39 years (late reproductive age), and 40+ years (perimenopausal and menopausal). Age groupings were based on similar research studies in reproductive health*.

Here are our three key findings:  

• LH levels were higher during the colder season among women aged 25-34 when compared to the late reproductive and menopausal age groups.
• E3G levels were lower during the hotter season among women aged 25-34 when compared to the late reproductive and menopausal age groups.
• PdG levels were higher during both the hot and cold seasons among women aged 40+ when compared to the mid and late-reproductive age groups. 

Previous research has shown a seasonal variation in hormone levels among different age groups. However, we still have a lot to learn when it comes to what those exact hormone levels look like and how their patterns may change as an individual ages. This study helps to further this gap in research.

*Afolabi et al., 2014 and Thiyagarajan et all., 2023

Making the Most of Your Personal Hormone Health

We know what the broader research says… but what does that mean for real people in their day-to-day lives? Here’s a quick look at how you can leverage these findings at home if you are TTC (trying to conceive).  

Monitor your hormone levels in real-time

With Mother Nature on your side, there is no better time to start monitoring your hormones than during the warmer months of the year. With regular hormone monitoring, you can maximize your chances of conception by ensuring that you plan sex at the right time each cycle. 

This can be done with the Mira App and Monitor, which can test for LH, E3G, and PdG. Mira is the only at-home monitor that combines the power of AI with lab-grade technology, providing individuals with their numeric hormone concentration measurements so they can get pregnant as efficiently as possible. 

To learn more about Mira’s technology, check out our article The Science of Hormone Tracking: 5 Proven Facts About Mira Technology. 

Take supplements – especially during colder seasons 

In addition to reducing our chances of conception, research also shows that natural dips in estrogen levels can make us vulnerable to feelings of low mood and depression. One way to combat this is with supplementation, particularly with vitamins B and D. According to UCLA Health, both vitamins can support the body with estrogen production – which in turn can help to improve our mood and fertility. 

If you’re looking for a TTC-friendly supplement, check out Mira’s own Prenatal Multivitamins and PCOS supplements. Both are formulated by fertility experts to support hormone balance and reproductive wellness. 

Continue learning about your hormones

Hormones control so many different aspects of our lives – from our metabolism, sleep, sex drive, fertility, mood, and so much more! 

If you would like to learn more about your hormones and how they impact your health, a great place to start is with our free Sex Hormones 101 e-book. 

If you feel that you need more in-depth, personalized support, we also offer one-to-one hormone health coaching where you can receive practical advice from an experienced fertility coach. From helping you interpret your Mira charts to providing lifestyle guidance and moral support, our fertility coaches are here to help you feel supported throughout your entire TTC journey. 

You can also check out our other (free!) resources including our regularly updated blog, webinars, and the Mira Fertility Club on Facebook. 

Final Thoughts

There is still a lot that we don’t know about our hormones. However, as testing methods improve, we can continue to learn more and more about the power of our hormones every day. 

If you’d like to learn more about Mira’s ongoing research projects with universities and organizations, check out our article Closing the Women’s Health Research Gap: 7 Inspiring Mira Research Collaborations.

You can also find our latest peer-reviewed publications and in-house studies in the research section of our website.