Every woman strives to have a healthy birth and baby by eating healthily and staying active, but there are some factors that aren’t solely in her control— such as the environment and pollution.  A new study published in the journal Environmental Health Perspectives found that babies in Beijing born to mothers in their eighth month of pregnancy during the 2008 Summer Games had  a statistically significant heavier birth weight than babies born a year earlier or a year later.

Of course, at that time in Beijing, the country underwent major changes to make lower pollution as the city prepared for and hosted the Olympics. They shut down factories, stopped construction and limited the number of vehicles allowed on roads for 47 days. Even in this limited time, the finding that babies were born healthier is significant.

This isn’t the first time air pollution has been tied to lower birth weight. In a 2004 study in Sao Paolo, Brazil, researchers found that increased exposure to carbon monoxide during the first trimester reduced birth weight by an estimated .8 ounces— similar to the Beijing study results.

In 2013, a large multinational study from 14 sites in nine countries found that for every 10-microgram increase of pollution particles per cubic meter of air, birth weight went down by roughly one-third of an ounce and infants were 3 percent more likely to be a low birth weight.

Babies who are born underweight— less than 5 pounds, 8 ounces— may be at a higher risk for multiple health issues, including delayed motor and social development or learning disabilities, according to the Centers for Disease Control and Prevention (CDC).

In the argument over global warming, one has to make the distinction that pollution especially affects birth weight. The means by which birth weight is affected is through the placenta. All of this carbon dioxide gets deposited into the placental tissues, which clogs adequate transfer of nutrients and oxygen to the baby— similar to how smoking can cause low birth weight.

As we discuss global warming, please keep in mind that countries have to do a better job in regulating pollution because it will ultimately affect generations to come.

Dr. Manny Alvarez serves as Fox News Channel's senior managing health editor. He also serves as chairman of the department of obstetrics/gynecology and reproductive science at Hackensack University Medical Center in New Jersey. Click here for more information on Dr. Manny's work with Hackensack University Medical Center. Visit AskDrManny.com for more.