Smoking during pregnancy increases the risk of many serious problems, including miscarriage, premature birth, premature placenta separation, low birth weight and sudden infant death syndrome.
Eleven per cent of pregnant women smoke, the Growing Up in New Zealand study found, but the rates are higher for women from deprived areas (17 per cent) and Maori women (34 per cent).
Dr Ho's programme allows the user to adjust the images to simulate the effects of smoking on levels of carbon monoxide and fetal movement. The current version is based on computer-designed human models, but the plan is to introduce images of smokers' own babies.
"The clinician," he said, "would collect the ultrasound images of the fetus, indicate to the software the files to use and the 3D model then morphs itself to resemble the real fetus. The clinician can then show various physiological and psychological simulations to explain smoking hazards."
Midwives, obstetricians and others would use the software as an educational tool in consultations to raise a woman's awareness of the harm of smoking in pregnancy and to trigger attempts to quitting smoking.
"Since pregnant smokers are often of low income and have lower levels of education, health literacy strategies that use digital graphics and the novel technologies can be of greater interest and thus influence."
Dr Ho said his group's work was based on earlier research demonstrating the high levels of poisonous carbon monoxide in an unborn baby's blood from a smoking mother, and a British study last year showing in high-tech ultrasound images the effects smoking may have on fetal facial movements.
The British researchers found the fetuses of smoking mothers showed a higher rate of mouth movements than normal. They suggested this might be because the fetal central nervous system did not develop at the same rate in the presence of smoking. Earlier studies had reported delayed speech-processing abilities in infants exposed to smoking in pregnancy.
Carbon monoxide in the fetal blood deprived the baby of oxygen, said turanga co-director Dr Marewa Glover, of Massey University. It also increased the blood's thickness, and this contributed to a slowing of growth.
