Maternal smoking during pregnancy has long been associated with congenital heart defects in offspring, but new research published this week in the European Journal of Preventive Cardiology suggests parental smoking during a mother's pregnancy — both maternal and paternal — increases risks in newborns.

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According to the Atlanta-based Centers for Disease Control and Prevention, CHDs are conditions present at birth that "can affect the structure of a baby's heart and the way it works." The condition affects nearly 1 percent (or about 40,000) births in the United States each year and are the leading cause of stillbirth worldwide. It's "thought to be caused by a combination of genes and other factors, such as things in the environment, the mother's diet, the mother's health conditions, or the mother's medication use during pregnancy," and smoking during pregnancy.

For the new study published on Saturday, researchers conducted a first-of-its-kind meta-analysis involving 125 studies through June 2018. The collection featured data on 137,574 babies with CHDs and 8.8 million prospective parents.

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According to the research, any parental smoking was associated with a risk of CHDs in newborns. Compared to no smoking exposure, the risk increased 74 percent for men smoking, 124 percent for passive smoking in women and 25 percent for active women smoking.

Exposure to secondhand smoke during pregnancy was found to be harmful during all stages of pregnancy and even before pregnancy.

"Smoking is teratogenic, meaning it can cause developmental malformations," study author Jiabi Qin of China's Xiangya School of Public Health said in a statement to Science Daily. "The association between prospective parents smoking and the risk of congenital heart defects has attracted more and more attention with the increasing number of smokers of childbearing age."

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Qin recommends both parents should be smoke-free when trying to conceive and try to stay away from smokers. Fathers-to-be, Qin added, “are a large source of secondhand smoke for pregnant women, which appears to be even more harmful to unborn children than women smoking themselves.”

Moving forward, Qin encourages employers to implement smoke-free environments and health care providers to continue educating about the hazards of smoking.

Read the full study at journals.sagepub.com.

According to the CDC, other risks of smoking during pregnancy include:
  • Smoking makes it harder to get pregnant to begin with.
  • Women who smoke during pregnancy are more likely to have a miscarriage.
  • Smoking while pregnant can also negatively affect the placenta, the source of the baby's food and oxygen.
  • Smoking can lead to babies being born too early or have low birth weight. This makes it more likely the baby will be sick and will have to remain in the hospital for a longer time.
  • Smoking during and after pregnancy is a risk factor of Sudden Infant Death Syndrome (SIDS).
  • Babies born to women who smoke are more likely to have a cleft lip or cleft palate.