Research carried out by Virginia Commonwealth University, found flavoured e-cigarettes caused particularly severe facial abnormalities.
A new study now says that exposure to e-cigarette vapour causes facial deformities in the developing babies of pregnant mice.
While doctors have touted vaping as a 'safer' alternative to smoking combustible tobacco cigarettes, evidence suggests that they are not without their own risks.
The new research, carried out by Virginia Commonwealth University, found that flavoured e-cigarettes caused particularly severe facial abnormalities, adding to mounting documentation that the sweetening agents have dangerous effects.
According to the study, e-cigs may well cause very similar facial birth defects to those seen as a result of cigarette-smoking.
The Virginia Commonwealth researchers have taken a particular interest in determining what birth defects might occur if pregnant women are exposed to the vapour, and whether they differed from those caused by cigarette smoke.
A pregnant woman's smoking habit has long been known to have the potential to cause a cleft lip or palate, and has also been shown to cause small but meaningful changes in the brains of developing babies in some cases.
The researchers, to test whether the same may be true for vaping used a special device on mice and found that when they bred those mice, they found that they carried fewer embryos to begin with than did the group of female mice that were not exposed to vapor.
Then, as those embryos developed, the researchers made 3D recreations of their facial structures by referencing important markers on CT scans of the unborn mice.
The areas around the embryonic mice's faces were developing to be shorter and narrower than they typically would be, regardless of whether or not the e-liquid used was flavoured.
But the mice whose mothers had been exposed to the nut flavoured e-cigarette vapour showed signs of much more dramatic abnormalities to the entire area surrounding their mouths, as well as in their jaws and cheek areas.
Notably, e-cigarette smokers tend to show particularly high levels of compounds from acrylonitrile, a toxin that can cause everything from skin blisters to nausea, dizziness, confusion and even death at extremely high exposure-levels.
Acrylonitrile has never been shown to cause birth defects in humans, however. The new study's authors have not revealed the names of the chemicals that may cause the abnormalities in animals.