Even for Sperm, There is a Season, Ben-Gurion University of the Negev Study

Autumn is the time of year most associated with bumper crops of new babies, and according to an Israeli study there may be a scientific reason for it: human sperm are generally at their healthiest in winter and early spring. Based on samples from more than 6,000 men treated for infertility, researchers writing in American Journal of Obstetrics & Gynecology found sperm in greater numbers, with faster swimming speeds and fewer abnormalities in semen made during the winter, with a steady decline in quality from spring onward.