ICYMI: Your baby's birth weight may depend on the weather.

When we think about climate change we often think of the environmental impact.

But what about the cute little babies?

Researchers have discovered that extreme hot and cold can affect the birth weight of babies. They just can’t figure out why.

A study published in the The Journal of Environmental Research found that expectant mothers who were exposed to unusually hot or cold weather during their pregnancies were more likely to give birth to babies with a low birth weight, even when they are born at full term.

The study looked at more than 220,000 babies born in 19 hopsitals in the US between 2002 and 2008. Average temperatures were measured during each trimester of the pregnancies and an average temperature was calculated for the whole pregnancy.

Extreme hot and cold was measured in reference to normal weather patterns in the area at which the birth took place, with a focus on the pregnancy’s exposure to weather that was atypical of the region.

The study’s results – obtained by Live Science ahead of publication – found that pregnant women who were exposed to unusually hot or cold weather in their second and third trimesters were 18-31 percent more likely to have low-birth weight babies when compared to women exposed to milder weather. The study also found that women exposed to unusual temperatures throughout pregnancy were more likely to give birth to smaller babies.

Study senior author Pauline Mendola, an epidemiologist at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) said while they aren’t sure why extreme weather affects babies in this way, it would make sense take action.

“Until we can learn more, it makes sense to reduce the amount of time that pregnant women are exposed to extreme hot or cold weather,” she said. “For example, pregnant women might try to avoid prolonged outdoor exposure to extreme heat or cold whenever possible.”

Researchers say the results are concering considering global climate change is expected to result in more extreme weather, saying, "these results highlight the need for more research as well as public health awareness of the potential adverse effects of extreme local temperature during pregnancy."

Further research is required to discover exactly how extreme weather needs to be to affect a baby's birth weight.

While logistically this advice may be difficult for pregnant women, the findings are another indicator about how global climate change is affecting humans as a species and something to keep in mind during additional research.