Mothers who smoke frequently are putting their children's respiratory health at risk.

According to a new study, exposure to maternal secondhand smoke can significantly increase a child's future risk of developing chronic obstructive pulmonary disease (COPD). COPD includes a group of lung diseases such as chronic bronchitis and emphysema that negatively affect airflow and breathing.

For this research, the team examined the survey responses completed by 5,729 men and women who were a part of the Tasmanian Longitudinal Health Study Cohort, which was started in 1968. The data included the participants' history of exposure to secondhand smoke as well as their personal tobacco use.

The researchers found that children with mothers who smoked at least 20 cigarettes per day had a 2.7 times increased risk of being diagnosed with COPD when compared to children who were not exposed to cigarette smoke early on in life. The researchers found that risk of COPD increased even more when the child who was exposed to secondhand smoke started smoking later on in life. Smoking in general is a risk factor for COPD.

"We now appreciate that the risk of COPD can be accumulated from sources other than personal smoking, where the negative consequences of a mother's smoking may continue through to later adult life," Jennifer Perret, the lead author of the study, said in a press release. "Our findings further strengthen the current recommendation for smoking abstinence, especially for pregnant women and young mothers."

This study's findings add to the growing evidence that secondhand smoke exposure at a young age can lead to an increased risk of COPD in adulthood. A 2012 study, which was published in Respirology, found that children who were exposed to secondhand smoke when they were growing up were more likely to develop COPD and other respiratory problems in adulthood.

The COPD Foundation reports that more than 24 million Americans suffer from COPD and at least 12 million are unaware that they have the condition.

The Centers for Disease Control and Prevention (CDC) states that infants who are exposed to secondhand smoke are more likely to have asthma attacks, ear infections, respiratory infections and sudden infant death syndrome. Older children who are exposed to secondhand smoke are more vulnerable to bronchitis and pneumonia.

The study's findings were published in the journal, Respirology.