However, according to Israeli scientists, it may also be due to the fact that sperm quality is at its peak during the winter and spring months and right now could be the optimum time for couples to try for a baby. The scientists say this could possibly explain why there are such a high proportion of births occurring during the autumn months of the year.
For the study, Professor Eliahu Levitas and his colleagues, from Ben-Gurion University of the Negev, analysed 6,455 semen samples obtained from men treated for infertility at their clinic between January 2006 and July 2009.
Writing in American Journal of Obstetrics & Gynecology, the researchers describe how they discovered that during winter there was evidence of sperm in greater numbers, faster swimming speeds and fewer abnormalities in the semen. After spring, the researchers claim there was a steady decline in sperm quality.
From the 6,455 samples, 4,960 had a normal sperm production, and 1,495 were defined as ‘abnormal’ which included factors such as a low sperm count. According to The World Health Organization, a normal sperm count is classified as at least 16 million sperm for each millilitre of semen.
It takes around 70 days for the body to generate a sperm cell and with this in mind, it was determined that men with a normal sperm production actually had healthier sperm during the winter season – producing about 70 million sperm per millilitre of semen during this period.
Delving a little deeper, it was found that around 5% of these sperm had ‘fast’ motility, which is the ability of a sperm to swim towards an egg. Ultimately this means there is a higher chance of a couple having a baby.
In comparison, during the spring time there was approximately 68 million sperm per millilitre of semen produced, and only 3% were found to be ‘fast’.
Interestingly though, a similar pattern was not evident for men with abnormal sperm production rates. In these men, better sperm was produced during spring and better motility began from autumn.
The researchers comment: “Based on our results the (normal) semen will perform better in winter, whereas infertility cases related to low sperm counts should be encouraged to choose spring and fall.”
Dr. Edmund Sabanegh, chairman of the urology department at Ohio’s Cleveland Clinic, was not involved with the study but says there have been similar trends in animals too in regards to their breeding seasons.
He says: “The hard part of this is really sorting out what factor is accounting for this.” Dr. Sabanegh does not believe that doctors will now specifically instruct men with infertility problems to wait until winter or spring to try and conceive a child. “We would continue to encourage them to try regardless of the season, and they may benefit from interventions or treatments.” Sedentary lifestyles and environmental factors could be connected to an overall decline in sperm quality for men around the world and Dr. Sabanegh added: “It’s becoming more certain that our fertility is seasonal and affected by complex things in our environment that change it.”
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