Blow to smoking mothers

Mothers who smoke in pregnancy may increase their child's risk of developing Crohn's disease, a debilitating bowel condition, new research shows.

Christchurch School of Medicine researcher Richard Gearry has been studying more than 400 patients with Crohn's as part of a wider look at inflammatory bowel disease (IBD).

At the first Canterbury Health Science Research Conference this week, Dr Gearry said a new risk factor for Crohn's disease had emerged from his study.

Genes play a role in whether someone will contract Crohn's but environmental factors are also significant.

Dr Gearry said it was known that smokers were more likely to develop Crohn's, but little research had been done into the impact of other kinds of exposure to smoke.

Dr Gearry found that mothers who smoked during pregnancy nearly doubled their child's risk of developing Crohn's later in life. No such link was found for ulcerative colitis, another form of IBD.

"Passive smoking hasn't been shown to be significant so far," Dr Gearry said.

Exactly why smoking might be linked to Crohn's was not known.

"There are lots of theories why. It may be that permeability of the bowel is increased by smoking or the blood supply is affected," he said.

It was known that breastmilk provided some protection from Crohn's. The longer infants were breastfed, the less their chance of developing the illness, which is usually diagnosed before the age of 30.

There has been a dramatic increase in IBD in New Zealand in recent years but researchers are puzzled why.

Some research has linked diets high in refined sugars and fat and low in fibre with inflammatory bowel disease while others have looked at the possible role of viruses and bacteria.

Dr Gearry has signed up 850 sufferers of IBD, out of an estimated 1200 in Canterbury. He is looking for more people to join his study, due to be finished next year.

- NZPA