Can the seasonal shifts impact fertility? There are a few studies that look at what time of year most women in the US conceive. They found that women typically conceive November-January. Now this could absolutely be related to women trying to time their pregnancies and have a baby in the summer. I think of teachers and women that are working and want more flexibility in the summertime, so this isn’t 100% related to being more fertile in the winter months but if we look at nature, it makes you wonder!
Reproduction is seasonal across all living organisms (including mammals). This is evolutionary where fall/winter is when conception happens and babies are born in the spring when more food is readily available. Of course, we have access to food all of the time now, so this isn’t a factor for humans now, but it would have been in the past. We also think about melatonin. In the winter months when the days are shorter and we have a lot more darkness, we also make a lot more melatonin, that is if we are blocking artificial light at nighttime, of course. Melatonin is mostly known as the hormone that helps you sleep well, but it’s also crucial for fertility.
Melatonin is a potent antioxidant, which means it helps protect cells from oxidative stress, including reproductive cells such as eggs and sperm. This protection can improve the quality of these cells, potentially enhancing fertility. In women, higher melatonin levels have been associated with better egg quality, particularly in older women or those undergoing assisted reproductive technologies like IVF.
Melatonin also impacts our reproductive hormones, including gonadotropin-releasing hormone (GnRH), which is crucial for the release of other reproductive hormones like luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones are critical for ovulation and sperm production.
In women, melatonin receptors are found in the ovaries, and the hormone is involved in folliculogenesis (the development of ovarian follicles). It can help regulate the timing of ovulation and support the luteal phase of the menstrual cycle, which is essential for implantation and maintaining early pregnancy.
In men, melatonin’s antioxidant properties can protect sperm from oxidative damage, improving sperm quality and motility. Some studies suggest that melatonin might enhance testosterone production, which is crucial for sperm production.
Male fertility is also seen to fluctuate with the seasons with lower levels of testosterone from August to October and higher levels of testosterone in the fall and winter months. This increases libido and can also optimize sperm quality and production. A lot of this is thought to be related to warmer temperatures and being exposed to excessive amounts of heat.
It can be tempting to want to take a supplement, but we recommend implementing specific lifestyle habits to support your body’s own production of melatonin:
You can learn more about supporting your circadian rhythm to optimize melatonin in our free fertility foundations audio series HERE!
reminder: i’m currently accepting people into my Nurture Your Fertility program. you can learn more here about the program and fill out an application!
