In-vitro mothers bloom in summer

MONTREAL - Women who undergo fertility treatment during the summer are twice as likely to become pregnant as when they try in winter, British researchers have found.

Longer daylight hours appear to improve the chances of successful treatment, says the study.

The research was presented at the annual conference of the American Society for Reproductive Medicine (ASRM) this week.

Dr Simon Wood and a team from the Countess of Chester Hospital in Ellesmere Port looked at more than 3000 cycles of fertility treatment carried out over a four-year period.

They studied women who had undergone cycles in both the summer months of April to September and the winter from October to March.

The pregnancy rate during summer was 15.7 per cent, compared with 7.5 per cent in the winter.

During the summer cycles, the women also needed lower doses of the drugs designed to stimulate ovaries prior to having embryos transferred.

"The results of this study appear to demonstrate the benefit of increased daylight length on outcomes of IVF cycles, " the team has concluded.

"Further research is required to confirm these findings and to identify the possible mechanism of action for the effect of extended daylight on reproduction."

Dr Wood suggested that one of the reasons may be evolutionary - it is known that mammals are more likely to conceive during the summer because it means their offspring will be born in the spring, when food is more plentiful, the weather warmer and they have a higher chance of survival.

This process is known as photoperiodism, and is linked to the hormone melatonin.

It is not known precisely how the hormone controls fertility, but melatonin regulates sleeping and waking cycles. It is produced during the night and suppressed during the day.

Experts had previously thought that women undergoing fertility treatment were immune to the impact of photoperiodism because the strong drugs they are given to stimulate their ovaries work to override Nature.

They believed that melatonin acted through the pituitary gland, which is "switched off" during IVF cycles.

Melatonin is found in receptors throughout the reproductive system and may be more important than previously thought, it has now been found.

Previous research has shown that women are also more likely to become pregnant naturally during summer and that vitamin D, derived from sunlight, can improve sperm quality.

- INDEPENDENT