A French study argues that tobacco use, even when terminated before pregnancy, can affect a woman’s placenta. According to the researchers, the placenta retains a kind of memory of exposure to tobacco.
Alterations in the placental genome
Tobacco affects the placenta in 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 from the University of Grenoble, the researchers studied the placental DNA of 568 women divided into three categories. The first concerned non-smoker women and the second women who quit 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. That is, the DNA sequence has not been altered, but gene expression may be. Moreover, these alterations were less present in former smokers. Nevertheless, in the latter, scientists have found alterations in 26 regions of the placental genome.
The “memory” of exposure to tobacco
“While a large number of regions appear to have a normal methylation profile in women after smoking cessation, the presence of some DNA methylation changes in the placenta of women who quit smoking before pregnancy suggests the existence of ‘an epigenetic memory of exposure to tobacco,’ Johanna Lepeule explained in a statement.
The placenta would therefore retain the “memory” of exposure to tobacco before pregnancy. Moreover, while 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 controlling the activation (or repression) of genes from a distance. 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 every cigarette smoked during pregnancy. As a reminder, around 20% of pregnant women smoke in Europe.