Is Spring the Best Time to Do an IVF Cycle?

a blog by Claire, July 17, 2012

Is the season of chicks and bunnies better than the other three for in vitro fertilization? The study "Seasonal variability in the fertilization rate of women undergoing assisted reproduction treatments," which is published in the July 2012 issue of Gynecological Endocrinology found that for couples undergoing IVF with intracytoplasmic sperm injection (ICSI), the fertilization — the joining of egg and sperm to form an embryo — rate was higher in the spring. Note: the season had no effect on pregnancy rates.

Brazilian researchers set out to determine whether seasonality affects assisted reproduction treatment outcomes. They studied 1,932 patients undergoing IVF/ICSI and grouped them by season according to the day of egg retrieval: winter (435 patients), spring (444) patients, summer (469 patients) or autumn (584 patients). All of the patients came from a single fertility clinic, the Assisted Fertilization Center in Sao Paulo – Brazil.

The researchers assessed fertilization 18 hours after ICSI, which is a procedure in which a single sperm is injected into the egg. They found that the fertilization rate increased during the spring:

• Spring: 73.5 percent
• Summer: 68.7 percent
• Autumn: 69 percent
• Winter: 67.9 percent

The researchers also measured hormone levels and noted that women's estradiol levels were higher in spring; however, the pregnancy rates did not change much during the seasons, remaining at around 33 percent.