In-vitro success rates much higher in spring

September 16, 2010

Debra Black

Staff Reporter
The Toronto Star

Spring is often associated with the blossoming of new love. It may also be the best time for in-vitro fertilization.
New research presented at the World Congress on Fertility & Sterility in Munich this week indicates that in-vitro fertilization is almost one and a half times more likely to be successful in March, April and May than in other months.
That may be due to the increased amount of daylight in those months and its impact on women’s hormones, said Dr. Daniela Braga, the lead researcher of the study, which was conducted at the Assisted Fertilization Center in Sao Paolo, Brazil.
“It has been suggested the fertility of animals is increased because of the length of the day,” she said in a phone interview from London. “That probably happens in humans as well.”
Braga, a former veterinarian, had noticed there is a seasonal breeding period in the animal world.
“I used to work with buffalo and cattle,” she said. “We know buffalos are seasonal breeders. We also have noted that there are other mammals that are seasonal breeders, as well as others that are not mammals, such as fish.”
She wondered if the same could apply with humans. So, Braga left her career as a vet, went back to school and studied human reproduction and the biotechnology of reproduction. She eventually joined the team at the Brazilian centre in Sao Paolo.
There, she and a team of researchers looked at the cases of 1,932 women undergoing egg retrieval for intracytoplasmic sperm injection (ICSI), a kind of in-vitro fertilization treatment, during all four seasons.
The results surprised her. While the percentage of developing eggs, high-quality embryos, implantation and pregnancy rates didn’t differ between seasons, the rate of fertilization did.
Specifically, the study found a 1.45-fold increase in the fertilization rate in the spring.
The researchers also measured the levels of different hormones in the female patients and found that the estrogen levels were significantly higher in the spring as well. That increase may be due to the increasing daylight in the spring, she said.
“It is possible that what we are seeing is the effect of changing light on the neurons in the brain which produce gonadotrophin-releasing hormones (GnRH).” That hormone controls the secretion of estrogen from the ovaries, she explained.
The study could ultimately improve the chances of some women getting pregnant, Braga said.
“In practical terms, this may mean that if you are having real difficulty in conceiving, it may be better to have an assisted-reproduction cycle during this season.”