4D ultrasound shows effects of smoking on unborn babies

Scientists found the fetuses of mothers who smoked touched their faces and moved their mouths more frequently while in the womb. Typically, unborn babies reduce these behaviours as they grow. The rate of decline of those movements was also slower in fetuses of smoking mothers.

That could indicate a delay in the development of the central nervous system, the study suggested.

The study's 24 participants were recruited from the antenatal unit at James Cook University Hospital in Britain. The four smokers on average smoked 14 cigarettes a day. The 4D ultrasound scans were conducted at 24, 28, 32 and 36 weeks through pregnancy. The study controlled for maternal stress and depression, but more research and a larger sample size were required to confirm the results, the authors said.

"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," concluded the report, which was published in the peer-reviewed medical journal Acta Paediatrica.

"Larger studies are required to confirm reported associations and further understand the relationship between maternal smoking, stress, depression and fetal development."

Previous studies have shown smoking while pregnant can increase the risk of stillbirth, miscarriage and premature labour. Smoking is also associated with underweight babies, which are in turn at risk of breathing difficulties, heart disease and infection.

One in seven Australian women smoke during some or all of their pregnancy, according to 2010 data from the Australian Institute of Health and Welfare. The figures were highest for teenagers mothers (37 per cent) and Indigenous mothers (48 per cent).

The most socio-economically disadvantaged women were almost four times as likely to smoke during pregnancy as those who were the least disadvantaged. And 17 per cent of Australian-born mothers smoked during pregnancy compared to 6 per cent for those born overseas.

The authors of the new study hoped their ultrasound images might discourage mothers from lighting up while pregnant, or motivate them to cut down.

"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," co-author Brian Francis, a professor at Lancaster University, told the British Telegraph.

"This is yet further evidence of the negative effects of smoking in pregnancy."