“A study identifies epigenetic changes in placenta related to maternal smoking during pregnancy”


Smoking during pregnancy is still common despite the increased awareness of adverse health consequences for the offspring. These early-life exposures may have long-lasting effects on child development.

One discipline that addresses this problem is epigenetics. Epigenetics studies several factors that can produce heritable changes in DNA without changing its sequence. Some studies have already assessed these type of changes associated to smoking during pregnancy, using cord blood. These studies have observed differential DNA methylation related to the detoxification of tobacco components, and even some of them have found that some effects of in utero exposure have persisted during childhood. Furthermore, some changes have been associated with low birthweight. However, few studies used placenta tissue, which may act as a record of in utero exposures, to assess DNA methylation.

For this reason, the present study of the Asturias, Gipuzkoa, Sabadell and Valencia INMA cohorts, examined whether smoking during pregnancy was associated with placental DNA methylation and whether these changes were related to low birthweight. A total of 427 mothers and their babies participated in the study, those with sufficient data to perform a Genome-Wide Association Study. The largest to date addressing this particular issue and including a rigorous validation and replication phase of the main results.

The study identified new regions in which changes related to smoking during pregnancy were observed. Furthermore, it pointed to several pathways that could explain these changes. One of the most remarkable findings was lower methylation in a region previously linked to fetal growth, lower birthweight and placental weight. These results indicate that smoking during pregnancy impacts specific placental changes. However, it is essential to carry out future research that replicates and validates the obtained results. Further research is necessary, which addresses the role that these specific DNA region changes can have in the relationship between smoking during pregnancy and the offspring.

Reference: Morales E, Vilahur N, Salas LA, Motta V, Fernandez MF, Murcia M, Llop S, Tardon A, Fernandez-Tardon G, Santa-Marina L, Gallastegui M, Bollati V, Estivill X, Olea N, Sunyer J, Bustamante M. Genome-wide DNA methylation study in human placenta identifies novel loci associated with maternal smoking during pregnancy. Int J Epidemiol. 2016 Oct;45(5):1644-1655.