These remarkable scans clearly reveal how smoking during pregnancy harms an unborn baby 's development . New ultrasound images show how babies of mothers who smoke during pregnancy touch their mouths and faces much more than babies of non-smoking mothers . Foetuses normally touch their mouths and faces much less the older and more developed they are . Experts said the scans show how smoking during pregnancy can mean the development of the baby 's central nervous system is delayed . Doctors have long urged pregnant women to give up cigarettes because they heighten the risk of premature birth , respiratory problems and even cot death . Now researchers believe they can show the effects of smoking on babies in the womb - and use the images to encourage mothers who are struggling to give up . Scroll down for video . Image shows the 4-D ultrasound scan of two foetuses at 32 weeks gestation , one whose mother was a smoker ( top ) and the other carried by a non-smoker ( bottom ) . The foetus carried by the smoker touches its face and mouth much more , indicating its development is delayed . As part of the study , Dr Nadja Reissland , of Durham University , used 4-D ultrasound scan images to record thousands of tiny movements in the womb . She monitored 20 mothers attending the James Cook University Hospital in Middlesbrough , four of whom smoked an average of 14 cigarettes a day . After studying their scans at 24 , 28 , 32 and 36 weeks , she detected that foetuses whose mothers smoked continued to show significantly higher rates of mouth movement and self-touching than those carried by non-smokers . Foetuses usually move their mouths and touch themselves less as they gain more control the closer they get to birth , she explained . The pilot study , which Dr Reissland hopes to expand with a bigger sample , found babies carried by smoking mothers may have delayed development of the central nervous system . Dr Reissland said : ' A larger study is needed to confirm these results and to investigate specific effects , including the interaction of maternal stress and smoking . ' She believed that videos of the difference in pre-birth development could help mothers give up smoking . Dr Nadja Reissland , of Durham University , said the ultrasound scans show unborn babies of mothers who smoke may have delayed development of their central nervous systems . But she was against demonising mothers and called for more support for them to give up . Currently , 12 per cent of pregnant women in the UK smoke but the rate is over 20 per cent in certain areas in the North East . All the babies in her study were born healthy , and were of normal size and weight . Dr Reissland , who has an expertise in studying foetal development , thanked the mothers who took part in her study , especially those who smoked . ' I 'm really grateful , they did a good thing , ' she said . 'These are special people and they overcame the stigma to help others . ' Co-author Professor Brian Francis , of Lancaster University , added : '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 . 'This is yet further evidence of the negative effects of smoking in pregnancy . ' The research was published in the journal Acta Paediatrica .
Scans reveal babies of mothers who smoke touch their mouths and faces much more than babies of non-smokers . Foetuses normally touch their mouths and faces much less as they become more developed closer to their birth . Comment: Researchers say the shocking images could be used to encourage pregnant women to give up smoking .