A French study argues that tobacco use, even in the case of termination before pregnancy, can affect a woman's placenta. According to the researchers, the placenta retains a sort of memory of tobacco exposure.
Tobacco affects the placenta of women. In any case, this is the conclusion of a study published in the journal BMC Medicine on October 7, 2020. Led by Johanna Lepeule of the University of Grenoble, the researchers studied the placental DNA of 568 women divided into three categories. The first concerned non-smoking women and the second women who had stopped smoking in the three months preceding pregnancy. The last category included women who continued to smoke before and during their pregnancy.
According to the results, there are so-called "epigenetic" alterations in 178 regions of the placental genome . More specifically, these are alterations in DNA methylation. In other words, the DNA sequence has not been modified, but the expression of genes may have been. Moreover, these alterations were less present in former smokers . Nevertheless, in the latter, the scientists found alterations in 26 regions of the placental genome.
“While a large number of regions appear to have a normal methylation profile in women after smoking cessation, the presence of certain DNA methylation changes in the placenta of women who quit smoking before pregnancy suggests the existence of an epigenetic memory of tobacco exposure,” explained Johanna Lepeule in a press release.
The placenta would therefore retain the "memory" of tobacco exposure before pregnancy. Moreover, if the harmful consequences of tobacco on the health of mothers are known, the mechanisms at work are much less so. In addition, the placenta is vulnerable to many chemicals. However, the researchers found that the altered regions of the placental genome correspond to areas that remotely control the activation (or repression) of genes. Obviously, this plays a very important role in the development of the fetus. According to Johanna Lepeule, the effects of smoking on the fetus and the subsequent health of the child could be explained by these epigenetic changes present in the placenta of smoking mothers.
In 2019, a US study highlighted how smoking contributes to the risk of sudden infant death syndrome. The risk of Sudden Infant Death Syndrome (SIDS) increases with each cigarette smoked during pregnancy. As a reminder, approximately 20% of pregnant women smoke in Europe.
