Seasonal Variation in Human Semen Quality
In regions with warm climates the birth rate is reduced during the spring season1–3. Could summer heat nine months earlier have caused semen quality to deteriorate and diminish the rate of conception? Human testes and epididymides, carried in the scrotal sac, are more likely to be influenced by environmental temperatures than are female reproductive organs, located inside the pelvic cavity and protected by the full complement of the body’s homeostatic mechanisms4. Even mild scrotal warming after two to three weeks can temporarily reduce both concentration and number of sperm in ejaculates5. A decrease in the frequency of sexual intercourse might account for a diminished rate of conception during summer, but the available evidence suggests, if anything, that the opposite may occur4,6–8.
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