Shocking new 4-D imaging show infants still in the womb cover their faces and cringe ever time their mother inhales a cigarette.

Prior research has shown that smoking while pregnant can increase the risks of miscarriage and premature labor. In addition, babies born to smoking mothers often are underweight and have difficulty breathing, heart problems, and infections.

The latest study published in the peer-reviewed online medical journal Acta Paediatrica, shows that smoking while pregnant can also harm the baby’s central nervous system.

The study was conducted in the prenatal ward of the James Cook University Hospital in Britain. 24 participants were given 4-D ultrasound scans at 24, 28, 32, and 36 weeks of pregnancy. Four of the participants admitted to smoking an average of 14 cigarettes per day.

The ultrasounds revealed that the fetuses touched their faces and frequently moved their mouths. Normally, as the baby grows, these behaviors occur less often. That the rate of decline of these movements in the fetuses of smokers is much slower than in nonsmoking mothers could indicate a delay in the development of the central nervous system.

“Over and above the effect of stress, smoking status had a significant effect on frequency of fetal mouth movements and a marginally significant effect on facial self-touch,” said the report in its conclusion.

A larger study, with a greater and more varied sample size, will need to be conducted to confirm the results. Yet it can not be denied that smoking is bad for an unborn child.

“Technology means we can now see what was previously hidden, revealing how smoking affects the development of the foetus in ways we did not realise,” said Brian Francis, co-author of the study and a professor at Lancaster University. “This is yet further evidence of the negative effects of smoking in pregnancy.”

The researchers hope that the images alone will encourage new mothers to quit smoking or at least reduce the amount of cigarettes they smoke per day.