Doctors have advised women who give birth during winter time to use a sun lamp during the final trimester so as to avoid the development of osteoporosis in their unborn babies.
The suggestion comes after a research found that children born to mothers whose final three months of pregnancy included a summer month were 40 percent less likely to suffer the bone-wasting condition in adult-hood.
A mother's exposure to sunlight in that final period ensures the developing baby receives enough vitamin D to form strong bones.
Doctors suggest that women whose last trimester of pregnancy does not fall between May and September should consider taking a holiday in the Mediterranean.
As flying is not advised in the late stages of pregnancy, however, they suggest that women may need to settle for a sun lamp or vitamin D supplements.
"You only get good sunlight [when you make vitamin D] between May and September in this country. Pregnant women should have vitamin D supplements or should have lots of good sunshine in somewhere like north Africa or the southern Mediterranean [in winter]," Times Online quoted Dr Marwan Bukhari, a consultant rheumatologist at the Royal Lancaster Infirmary, as saying.
Bukhari added: "Sun lamps are an option. It needs to be the right kind of sun lamp to convert fat under the skin to vitamin D."
The doctors are not recommending sunbeds, which give a far higher dose of ultraviolet light than lamps.
In the research, the research team studied 17,000 patients, mostly women and 95 percent of whom were white. They had all had scans carried out at the Royal Lancaster Infirmary between 1992 and 2004.
They found that patients under 50 were 40 percent less likely to have developed osteoporosis if their mother's last trimester of pregnancy included a summer month.
Older patients were 20 percent - 40percent less likely to have osteoporosis if their mothers' late stages of pregnancy were in the summer.
The study will be presented to the British Society for Rheumatology.