Second-hand smoke from fathers puts unborn babies at risk of heart defects

Fathers who smoke can put their unborn children at risk for congenital heart defects (CDs), according to a study reported by scientists from the Xiangya School of Public Health, Central South University, in Changsha, China. The research, carried out as a meta-analysis of data from 125 studies involving more than 100,000 children with coronary artery disease, showed that maternal active smoking, maternal passive smoking and paternal smoking all increased the risk of coronary heart disease in the child. offspring. “Expecting fathers should quit smoking,” commented the study’s lead author, Jiabi Qin, PhD, who leads the team from Central South University. “Fathers are a big source of second-hand smoke for pregnant women, which appears to be even more harmful to unborn children than women who smoke themselves.”

The researchers describe their study and findings in the European Journal of Preventive Cardiologyin an article entitled “Parental smoking and the risk of congenital heart defects in offspring: an updated meta-analysis of observational studies”.

Congenital heart defects affect around 8% of live births worldwide and are a leading cause of death in newborns, the authors wrote. The prognosis and quality of life are improving thanks to innovative treatments, particularly surgery, but the effects on affected children nevertheless last a lifetime. Smoking is known to pose a risk to normal fetal development, Qin noted, and there is growing interest in the potential link between parental smoking and heart defects in their offspring. “Smoking is teratogenic, meaning it can cause developmental malformations,” Qin said. “The association between smoking by expectant parents and the risk of congenital heart defects is gaining increasing attention with the growing number of smokers of childbearing age.”

However, the authors pointed out that although there have been many studies assessing the risk of coronary heart disease associated with maternal passive smoking and paternal active smoking, the results have been inconsistent. Further, they pointed out, reviews of studies investigating the relationship between smoking and coronary heart disease in offspring have primarily focused on maternal active smoking, “…and have not examined either the relationship between maternal passive smoking and coronary heart disease or the relationship between paternal smoking and coronary heart disease… In fact, maternal passive smoking and paternal smoking are more common than maternal active smoking. did not take into account the time of exposure to smoking. “The critical stage in the development of the fetal heart occurs in early pregnancy. Therefore, it is very important to focus on the association between parental smoking before pregnancy or in early pregnancy and coronary artery disease, which may help explain causation,” Qin’s team said.

To try to provide a more comprehensive assessment of the effects of smoking on coronary artery disease in offspring, the team designed an updated meta-analysis of observational studies to assess the link between active and passive maternal smoking, as well as the paternal active smoking, on different types of CHD. They identified 125 eligible studies published between 1971 and 2018, involving 137,574 coronary artery disease cases and 8.8 million expectant parents.

The results of their analyzes indicated that, compared to no exposure to cigarette smoke, all three types of parental smoking were associated with an increased risk of coronary artery disease in the offspring. “Our results suggest that maternal passive smoking and paternal smoking were also significantly associated with the risk of fetal coronary artery disease, which was not confirmed by previous meta-analyses,” the team wrote.

The greatest risk of coronary heart disease risk was associated with maternal passive smoking. “The results of the present meta-analysis indicated that parental smoking was significantly associated with the risk of coronary artery disease in the offspring, with an increased risk of 25% for maternal active smoking, 124% for maternal passive smoking and 74 % for paternal active smoking, compared with non-smokers,” the authors reported. Interestingly, the association between CAD risk and all types of parental smoking was higher when the analysis was restricted to Asian populations.

Looking at different types of congenital heart defects, the researchers’ analyzes also indicated that maternal smoking was associated with a 27% increased risk of atrial septal defect and a 43% increased risk of right ventricular outflow tract. “…our review found no statistically significant differences for the risks of other CHD subtypes between comparison groups,” the researchers wrote. They were also unable to assess the relationship between maternal passive smoking or paternal active smoking and coronary artery disease subtypes because there were too few studies of each type of coronary artery disease.

The scientists suggested their review represents the most up-to-date on the subject, and its large sample size provides more accurate and reliable risk estimates than previous studies. It is also the first review to investigate the effects of smoking at different stages of pregnancy on the risk of coronary artery disease. These data indicate that a woman’s exposure to someone else’s cigarette smoke even before pregnancy puts her unborn child at risk of developing coronary heart disease. In contrast, while the offspring of women who smoked during pregnancy had an increased risk of coronary artery disease, active maternal smoking before pregnancy did not affect the risk of coronary artery disease.

“Women should quit smoking before trying to get pregnant to make sure they don’t smoke when they conceive,” Qin said. “It’s also important to stay away from people who smoke. Employers can help by ensuring workplaces are smoke-free. “Physicians and primary health care professionals need to do more to educate and educate expectant parents about the potential dangers of smoking to their unborn child.”

The team noted that the exact mechanism involved in the association between parental smoking and coronary heart disease in their offspring is unclear and will require further research. Nevertheless, they pointed out, some previous studies have indicated that maternal passive smoking has more harmful factors than maternal active smoking, “which was basically consistent with this study,” the team commented. “However, the mechanism of association between parental smoking and coronary heart disease risk still needs to be explored further.”

The researchers acknowledged that their study has several limitations. Nevertheless, they concluded, “…our study indicated that active and passive maternal smoking, and paternal active smoking, are associated with a higher risk of coronary artery disease…the prevention of parental smoking during peri-pregnancy is a priority for the prevention of coronary heart disease”.