Women who smoke during pregnancy greatly increase the risk their child will develop a life-threatening cancer, a new Australian study shows.

Researchers assessed more than one million births recorded across NSW from 1994 to 2005, and found 948 cases in which the growing child went on to develop a cancer.

Professor Jim Bishop, chief executive of the Cancer Institute of NSW, said 17 per cent of Australian women admit to smoking during their pregnancy.

"There is more and more evidence accumulating that pregnancy and smoking don't go together," Prof Bishop says.

The study found babies with a low birth-weight had 1.7 times the risk of developing leukaemia and 1.8 times the risk of developing cancer of the brain or central nervous system.

Newborns in need of ICU care were at most risk - their chance of developing any cancer was 2.7 times increased while for eye cancer the risk was four times, five times for kidney cancer.

Prof Bishop said smoking during pregnancy was not the only cause of premature birth or other health complications in newborns.

"But it is clear that we can do something about those complications - that is not to smoke during pregnancy," he said.

Children born to smokers also had higher rates of asthma, Prof Bishop says.

NSW Medical Research Minister Jodi McKay said the number of Australian women who smoked during their pregnancy was "alarming".

"Everybody knows that smoking causes cancer, stroke, heart disease and emphysema but all mothers and mums-to-be should also understand the potential damage to a child caused by prenatal smoking," she said.

Source : 2009 AAP