Biological explanation of lower birth weight from smoking during pregnancy

New-born babies of smoking mothers weigh on average 200 grams less than the babies of non-smoking mothers. Nearly 20 percent of this lower birth weight can be accounted for by the change in DNA methylation of the GFI1 gene as a result of smoking during pregnancy. This is the conclusion of a study conducted at the University Medical Center Groningen. According to the study, these findings are confirmed by research conducted by the Erasmus MC in Rotterdam and the University of Bristol in England. The researchers are publishing their results this week in the International Journal of Epidemiology.

In a genome-wide methylation study among 255 children, the researchers investigated whether smoking during pregnancy leads to differences in DNA methylation in the child’s umbilical cord blood. DNA methylation changes the extent to which genes are expressed without changing the DNA itself. This change in gene expression can in turn result in other changes, such as a lower birth weight.

Lower birth weight

Earlier studies showed that exposure to cigarette smoke during pregnancy can change the child’s methylation pattern. Thus far it was not known whether these changes in DNA methylation could also account for the lower birth weight. The present study shows that children of smoking mothers are on average 202 grams lighter at birth and that 12 to 19% of this lower birth weight can be accounted for by differences in DNA methylation of the GFI1 gene. The GFI1 gene plays a role in growth and development.

Cardiovascular diseases

‘Our study clearly shows the negative effects of smoking during pregnancy for the child’s development. A too low birth weight increases the risk of developing conditions such as cardiovascular diseases or diabetes at a later age. It goes without saying that these negative effects can be prevented if pregnant women are made aware of the importance of quitting smoking. We therefore hope that our study can contribute to partially clarifying the biological effects of smoking during pregnancy,’ says Leanne Küpers, PhD students who conducted the study. She also found that other genes are impacted by smoking during pregnancy. ‘But in the context of our study, these genes did not seem to account for the lower birth weight.’

GECKO Drenthe Study

The study forms part of the GECKO Drenthe Study. This large-scale study follows 2,900 children born in Drenthe in 2006 and 2007. In close collaboration with GGD Drenthe (Municipal Health Centre), the researchers carry out frequent length and weight measurements and investigate lifestyle factors. The study aims to identify which factors play a role in the development of overweight in children.