It's common knowledge that mothers should not smoke while pregnant. But the actual mechanism behind what is going on in the womb is, surprisingly, not well understood.
New research changes that, finding that a major reason unborn babies are harmed by smoking is due to free radicals and unwanted molecules moving around the mother's body.
This new research is an international project between the University of Technology Sydney (UTS), Chulalongkorn University in Bangkok, and the Kolling Institute in Australia.
"Prior to the study, it was thought that nicotine caused most adverse effects on the health of mothers and their offspring," said lead researcher, Brian Oliver from UTS.
"When a person smokes, however, additional toxic chemicals and billions of free radicals (oxidants) are inhaled, enter the blood stream and affect the whole body."
It isn't just the lungs that are then affected. The molecules, known as free radicals, have already been shown to cause damage to our whole bodies – and can lead to cancer.
"Free radicals are molecules like hydrogen peroxide (H2O2) that are highly reactive and can chemically change (similar to bleaching) tissues in the body. For pregnant women, the response to these chemicals extends to the developing child," Oliver added.
Human studies have already shown that maternal smoking is associated with damaged lung development, airflow limitations and an increase in the risk of respiratory infections.
But now we have more of an idea why this is the case which is important for scientists to be able to explore if and how they can limit the damage.
Especially considering this is also an issue for women living in high pollution areas, or use other forms of nicotine, that aren't traditional smoking such as e-cigarettes. The researchers are now investigating these areas.
The research has been published in American Journal of Physiology - Lung Cellular and Molecular Physiology, and was included in the APS Select, a collection of outstanding research from the society.
UTS Science is a sponsor of ScienceAlert. Find out more about their research.