Sperm Healthiest in Winter, Early Spring

Study finds robust sperm counts in these months explain higher birth rate in the fall.

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Sperm are not suffering from the winter blues, according to a study out of Israel last year. Researchers say that human sperm are generally at their healthiest and "swim" faster in winter and early spring, making it easier to conceive during those months.

Researchers found that sperm concentration and the percentage of fast motility — the ability to move spontaneously and independently — decreased significantly from spring into summer and fall, rebounding in the winter and early spring. The physical structure of the sperm cells was also the healthiest in the winter and early spring months, according to the study published in the American Journal of Obstetrics & Gynecology.

Researchers tested 6,455 semen samples over the course of three years. The robust sperm counts in these months would explain the higher birth rate in the fall, which means higher conception rates the previous winter and early spring.

For example, the subjects in the study produced about 70 million sperm per milliliter during the winter and 68 million per milliliter in the spring, of which 5 and 3 percent respectively were considered to have "fast" motility. (Fast motility, or swimming speed, is a factor in improving the odds of conception.) The World Health Organization defines anything over 15 million sperm per milliliter of semen as a normal sperm count. Researchers noted that more studies are necessary to find the exact link between the time of the year and sperm health, but some experts suggest hormone variations and exposure to daylight as possible factors.

Nearly half of all fertility troubles are linked to sperm problems. Learn more about what a guy can do—and what he should avoid doing—to maximize his fertility and his chances of making plenty of hardy, healthy, fast-swimming sperm.

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