New research out of Norway suggests pregnant women who spend a lot of time in the sun may inadvertently harm the longevity of their children.

The findings, published in the journal Proceedings of the Royal Society B, are based on an analysis by researchers from the Norwegian University of Science and Technology of church records of more than 9,000 people from 1750-1900 and historical cycles of solar radiation.

The results showed the average lifespans of children born in years that had a great deal of solar activity (including more heavily concentrated UV rays) were 5.2 years shorter than other children, Yahoo.com reports.

What’s more, Norwegian children born during high-UV periods, whose mothers spent a lot of time outside, were much less likely to make it to age 2 than those burn during less intense periods.

In accounting for the trend, the researchers suggested UV radiation can have positive effects on our vitamin D levels, but also results in a degradation of vitamin B9 — folate, which is required for DNA synthesis, rapid cell division, and cell growth during pregnancy.

“Our results indicate that too much sunbathing while pregnant may have detrimental effects on the fetus’ survival and subsequent reproductive performance,” said study co-author Gine Roll Skjærvø, a biologist.