Sperm prefer winter

With this interminable winter, here is something to restore balm to the hearts of French couples. While a recent study noted the significant decline in French sperm, Israeli researchers from Ben-Gurion University in the Negev have just made a surprising finding which they reported in the American Journal of Obstetrics and Gynecology. Their study shows that the sperm human is most fertile during the winter months and until the beginning of spring.

Thus, between January 2006 and September 2009, these researchers collected and passed under a microscope 6,455 sperm samples from men in couples who were unable to conceive children. Among these samples, 4,960 of them showed no signs of concern, while the remaining 1,495 contained less than 15 million spermatozoa per ml of semen, criterion of theWHO to define infertility.

Results of the analysis, it was during the cold season that the sperm were found in greater number, that they were faster and less deformed in fertile men. For example, in winter, they had 70 million gametes per ml, 5% of which are particularly mobile and good swimmers, which increases the chances of fertilization. In the spring, the numbers fell by 2 million per ml, and the proportions of very active spermatozoa increased to 3%.

However, this pattern was not observed in infertile men. For them, the speed records were broken in the fall, but it was in the spring that their sex cells were best formed.

Even though this research does not provide the underlying biological explanations, scientists are making some assumptions based on animal studies. The amount of semen would decrease as temperatures rise, possibly due to exposure to the sun. And, hormonal variations are also being considered by these researchers.
This new study therefore seems to explain why there are more births between the months of May and September. Last year, in France, INSEE reported that more than 403,000 babies were born between June and November while they were only 387,000 between December and May.