Sperm: they prefer the winter!

An explanation is found throughout the cold: . Winter is, in Sapiens, the mating season 1Because the figures of the National Institute of Demographic Studies (INED) show unambiguous: the period when more children are born from July to October, with a peak in September.

Especially around 23 September, where births are twice as likely than a normal day, but that peak one has a very special explanation, since it corresponds to concepts of Eve, the night of New Year festivities !

Apart from this feast day , simply subtract nine months birthday to find that lots of little Jesus are designed in winter. Because it is cold and couples looking to keep warm in the arms of one another?

Science, which never satisfied appearances, has recently been a much better explanation! One explanation lies in one word: sperm. For Israeli researchers made the finding that male reproductive cells have a strong preference for the winter season: it makes them strong …!

That was in 2013, at University Medical Center Soroka (Beer-Sheva, Israel) . The protocol? It covered nearly 6500 samples of sperm of men who had consulted the procreation aid department with their partner.


The result ? In winter, in healthy men, the sperm were more numerous, better trained and more particularly mobile! This last feature is crucial since only a very small number of sperm can swim fast enough to reach the egg of the mother.

However, while in spring and summer, these high-performance swimmers were only 3.5 to 4% in the samples studied, in the fall, they reached 4.9% and 5% … in winter! An increase of 43% compared to the spring.

Who would have suspected that male gametes are at their best in the cold season! But the facts are there: winter is conducive to reproduction, paternal side. And logically, births registered in the same Israeli hospital were significantly higher in the months from July to October, nine months after the cold season.


Of course, one question burns the lips: what may well hold this seasonal variation in sperm quality?Las biologists do not really explain. However, as noted by Dr. Jacques Auger, reproduction biologist at the Cochin Hospital (Paris) , the phenomenon is known since the early 2000s!

A study published in 2001 and conducted in several European cities (Paris, Edinburgh, Copenhagen …), but on a smaller number of men in the Israeli study had found a better sperm quality winter: sperm concentrations were 30% higher than it was!

“This could be due to variations in sunshine during the season , which would influence the hormones and so on sperm production … but there is still no proof” , explains the researcher.

Better understanding these mechanisms would however be useful, especially for couples struggling to have a child. In France, they account for nearly one in five couples.


According to Science & Vie Q & A # 14