Exposure to sunlight can boost the likelihood of a woman having a baby much as a third, according to scientists.
Couples hoping to conceive may find that heading to sunnier climes may improve their chances, according to experts.
Fertilisation rates, live births, and the number of eggs all improved after women were in the sun.
Scientists studied the IVF results of 6,000 women over a six-year-old period, and analysed them alongside the weather conditions in the month before women started treatment.
During the least sunny periods, live birth rates were 14 per cent, but this figure rose to 19 per cent when the weather improved, The Telegraph reported.
Dr Frank Vandekerckhove, a Belgian researcher from the University Hospital Ghent’s Centre for Reproductive Medicine, presented the study at the European Society of Human Reproduction, and told the conference that sunshine, high temperatures and the absence of rain made treatments more effective.
He added that while the study involved IVF patients, the results also apply to women who want to get pregnant without assistance, The Huffington Post reported.
In months with around four hours of sunshine a day, fertility was boosted by one third, however the figure stopped rising at six hours.
Women were 35 per cent more likely to have successful IVF treatments if they were exposed to pleasant weather a month before, rather than at the time of conception.
Vitamin D was likely a key factor in the positive hike in fertility rates as it affects the quality of eggs produced, while the hormone melatonin, which helps the reproductive cycle, was also a factor.
Prof Charles Kingsland, from Hewitt Fertility Centre, at Liverpool Women's Hospital, told the Telegraph that the study raises interesting points about how couples often get “bogged down” by “pills and potions”.
“Often all that is needed are the basics. Namely, good diet, no smoking, reduction in alcohol, relaxation, sunshine, be happy and positive - oh and finally, occasional sexual intercourse,” he said.
The research revealed that sperm is more active in the middle months of the year, and twice as active in July and August compared to January.