The impact of heat waves on fertility

As summers become hotter and heat waves more frequent, many people are starting to ask an important question: can extreme heat affect fertility? Research suggests that prolonged exposure to high temperatures may influence reproductive health in both women and men, particularly when heat stress becomes ongoing or severe.

While many heat-related fertility effects are temporary, understanding how heat impacts the body can help you take practical steps to protect your reproductive health during warmer months.

Effects of Heat on Female Fertility

Impaired ovulation

High temperatures can disrupt the delicate hormonal balance needed for regular ovulation. Heat stress may interfere with the signals between the brain and ovaries that regulate the menstrual cycle, potentially leading to irregular periods, delayed ovulation or reduced fertility.

Decreased egg quality

Emerging evidence suggests that heat-induced oxidative stress may damage the genetic material within eggs, reducing their viability for fertilisation. Oxidative stress occurs when the body produces more unstable molecules (free radicals) than it can effectively neutralise.

Researchers are still learning exactly how heat affects female fertility in humans, but studies indicate that elevated temperatures may impair ovarian function and compromise oocyte (egg) quality.

Inhibited implantation

Successful pregnancy depends on a receptive uterine environment. Elevated temperatures may interfere with implantation by affecting blood flow, hormone regulation and the lining of the uterus, making it more difficult for a fertilised egg to implant successfully.

Reduced cervical mucus

Heat and dehydration can reduce both the quantity and quality of cervical mucus. This fertile mucus plays an important role in helping sperm travel through the reproductive tract to reach the egg. When cervical mucus becomes thicker or less abundant, conception may become more difficult.

Effects of Heat on Male Fertility

Reduced sperm quality

Male fertility is particularly sensitive to temperature changes. Prolonged heat exposure can decrease sperm count, motility (movement) and morphology (shape), reducing the chances of successful fertilisation.

Even relatively small increases in testicular temperature may negatively affect sperm production.

Increased DNA damage

Heat-related oxidative stress can damage sperm DNA, potentially increasing the risk of infertility or miscarriage. Importantly, the effects of heat on sperm are not always immediate.

Because sperm production takes approximately 72–90 days, heat exposure today may affect sperm quality for up to three months afterwards.

Testicular overheating

The testes sit outside the body because sperm production requires a slightly cooler temperature than normal body temperature. Excessive environmental heat can disrupt this natural cooling mechanism, impairing the production of healthy sperm.

Frequent use of hot tubs, saunas, heated seats and prolonged exposure to high outdoor temperatures may all contribute to testicular overheating.

What You Can Do: How to Protect Your Fertility This Summer

Stay cool

Avoid prolonged exposure to extreme heat where possible. Seek shade, use fans or air conditioning and wear lightweight, breathable clothing. Men trying to conceive should avoid excessive use of hot tubs and saunas.

Stay hydrated

Dehydration can worsen the effects of heat on fertility. Drinking plenty of water supports overall reproductive health and helps maintain healthy cervical mucus production.

Rest during peak heat

Avoid strenuous exercise or outdoor activity during the hottest parts of the day. Spending time in cooler environments helps your body maintain the stable internal temperature required for healthy reproductive function.

Eat antioxidant-rich foods

Fruits, vegetables, nuts and other antioxidant-rich foods may help combat oxidative stress caused by heat exposure. Nutrients such as vitamins C and E, selenium and zinc have been studied for their potential role in supporting reproductive health.

Protective clothing for men

Loose-fitting underwear and breathable clothing can help maintain lower testicular temperatures and support healthy sperm production.

Prioritise sleep

Poor sleep caused by hot nights can disrupt the hormonal rhythms involved in fertility and reproductive health. Keeping your bedroom cool and maintaining a consistent sleep schedule may help support hormone regulation.

The Good News

In many cases, heat-related fertility changes are temporary. Once heat exposure is reduced, sperm quality often recovers within three to six months, and hormonal balance in women can stabilise over time.

If you are trying to conceive and are concerned about the effects of heat, prolonged irregular cycles or ongoing fertility issues, it may be helpful to speak with a healthcare professional or fertility specialist.

References

1. Northwestern University / Zhou, L.T. et al. (2024). The Effects of Heat Stress on the Ovary, Follicles and Oocytes: A Systematic Review. Available via PMC/NIH.
2. Li, J. et al. (2016). Heat stress and human reproduction: effects and pathogenesis. Published in Theriogenology and referenced in ScienceDirect reviews on heat stress and reproduction.
3. University of Oregon (2020). UO researchers show why heat stress damages sperm. Published in Current Biology and reported via ScienceDaily.
4. Moustakli, E. et al. (2025). Dietary and Lifestyle Interventions to Mitigate Oxidative Stress in Male and Female Fertility. Published in Metabolites.
5. Wang, X. et al. Changes in Levels of Seminal Nitric Oxide Synthase in Fertile Men after Scrotal Heat Stress. Available via PMC/NIH.