TAMPA, Fla. (WFLA) — Summer weather comes with visions of barbecues, beaches, and possibly tans, but a new study from Boston University reports that one potential effect of summer sun and heat may also put mothers at a higher risk of miscarriage.

The study said, currently, around 30% of pregnancies end in miscarriage, also called “spontaneous abortions.” The university conducted the study to identify some risk factors for the losses, because “few” have been determined.

The study, published in scientific journal Epidemiology, examined how different seasons could affect pregnancies in regions of North America. The study found that there was a 44% higher risk of early miscarriage during summer months. The study said early miscarriages were those that occurred within the first eight weeks of pregnancy.

For the comparison, the study authors pit late August against early February. The study found that the risk of miscarriage rose 31% in August, compared to February’s risk. Additionally, “the results showed that pregnant people in the South and Midwest, where summers are hottest, were more likely to experience this loss in late August and early September, respectively.”

“Any time you see seasonal variation in an outcome, it can give you hints about causes of that outcome,” study lead and corresponding author Amelia Wesselink, research assistant professor of epidemiology, said in a release from the university. “We found that miscarriage risk, particularly risk of ‘early’ miscarriage before eight weeks of gestation, was highest in the summer. Now we need to dig into that more to understand what kinds of exposures are more prevalent in the summer, and which of these exposures could explain the increased risk of miscarriage.”

“Almost 20% of women experienced spontaneous abortion,” the study results showed. “Risk was highest in late August.” The study said “the seasonal pattern was evident almost exclusively for spontaneous abortion” at less than eight weeks after a woman’s last menstrual period date. The “associations were stronger among women living in the Southern and Midwestern United States,” according to BU.

Of the 6,104 mothers in the study, 1,188 reported miscarriages, with the median gestational period being six weeks for the loss to occur.

Announcing the study results, a publication by BU said the research needs to be expanded to provide opportunities to better understand how extreme heat and other hot-weather factors could potentially result in “unexpected pregnancy losses.”

Study author Wesselink said, when providing the study results to WFLA.com, that the authors “saw higher risk in the summer” for seasonal miscarriage risks. The study did not examine factors such as weather or heat directly.

“We know that heat is associated with higher risk of other pregnancy outcomes, such as preterm delivery, low birth weight, and stillbirth, in particular,” Wesselink says. “Medical guidance and public health messaging—including heat action plans and climate adaptation policies—need to consider the potential effects of heat on the health of pregnant people and their babies.”