A groundbreaking French study reveals that smoking, even if stopped before pregnancy, can leave lasting epigenetic marks on a woman's placenta. Researchers suggest the placenta retains a 'memory' of prior tobacco exposure.
A study published in BMC Medicine on October 7, 2020, led by Johanna Lepeule from the University of Grenoble, examined placental DNA from 568 women divided into three groups: non-smokers, those who quit smoking in the three months before pregnancy, and those who smoked throughout pregnancy.
The findings identified epigenetic alterations—specifically DNA methylation changes—in 178 regions of the placental genome. These changes affect gene expression without altering the DNA sequence itself. Former smokers showed fewer alterations, but still had changes in 26 genomic regions.
“While many regions normalize after quitting, the persistence of certain DNA methylation changes in ex-smokers' placentas points to an epigenetic memory of tobacco exposure,” Lepeule explained in a press release.
This suggests the placenta remembers pre-pregnancy smoking. While tobacco's risks to maternal health are well-known, its placental effects are less understood. The altered regions regulate distant gene activation or repression, crucial for fetal development. Lepeule posits these changes may explain smoking's impact on fetal growth and later child health.
A 2019 U.S. study linked prenatal smoking to higher sudden infant death syndrome (SIDS) risk, increasing with each cigarette. Notably, about 20% of pregnant women in Europe smoke.
