Extreme cold kills more people than extreme heat, and it does so in a variety of ways.

You could freeze to death. You could be spending more time inside, picking up all sorts of nasty respiratory infections. More often, though, frigid temperatures get you in an even sneakier way: Cold weather causes arteries to constrict and blood to become thicker, increasing chances of having a heart attack or stroke. The winter months usually see a peak in various types of heart diseases, including heart attacks.

Weight, fitness, and lifestyle factors all contribute to the likelihood of having a heart attack during a cold snap, of course. But now, it looks like there's another cause—one far beyond your control. There’s evidence that your risk of dying of heart disease in the cold could depend on the temperature at which you experienced life as a fetus.

A forthcoming study in Social Science and Medicine shows that people who were in utero during the warmer months were more likely to die from this type of wintertime heart disease during cold periods.

For the study, researchers from University of California at Irvine, the University of California at Berkeley, and the University of Mannheim, Germany examined 13,500 Swedes born in Uppsala, a town just north of Stockholm, between 1915 and 2002. They then matched up their birthdays with the outside temperatures during the times they were gestating.