Spring is seen as a time of growth, renewal, and new life. So it's very fitting that this is the most successful time of year for vitro fertilization.

Research published in July's Gynecological Endocrinology found the rate of fertilization was significantly higher in spring than any other season. Unfortunately for mothers trying to concieve naturally, the study found no difference in pregnancy rates.

It is believed however, that the number of hours of sunlight in the day and temperature variations can affect fertility.

Researchers compared seasonal fertilization rates in 1932 women who underwent sperm injection, in Brazil from 2005 to 2009. ICSI involves the injection of a single sperm directly into an unfertilized egg, outside of a woman's body.

Subjects were organized into groups according to the timing of egg retrieval: 435 were assigned to winter, 444 to spring, 469 to summer and 584 to autumn. Fertilization, the fusion of sperm and egg to form an embryo, was assessed 18 hours after the procedure.

Ovarian response to the hormone treatments, a measurement of estrogen concentration per number of retrieved oocytes, was higher in spring compared with other seasons, tests showed. The rate of fertilization was 73.5 percent in spring, 68.7 percent in summer, 67.9 percent in winter and 69 percent in autumn.