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Last updated on April 24, 2014 at 6:16 EDT

Study Finds Smoking Gene Linked To Pregnancy

May 15, 2009

UK researchers show that a gene can explain why some women find it more difficult to stop smoking during pregnancy, BBC News reported.

The “addictive gene” was associated with a lower chance of quitting once pregnant, according to a study of 2,500 women who smoked before falling pregnant.

In the first three months of pregnancy it found that 28 percent of pregnant smokers quit compared with 21 percent of those with two copies of the gene and 31 percent without the gene.

There is no reason why the finding would not also be true in other groups of smokers attempting to quit, said researchers from Peninsula Medical School.

However, the team wanted to look at pregnant women because they have a particularly strong incentive to break the habit.

Researchers analyzed the Avon Longitudinal Study of Parents and Children, which collected data on 7,845 women of European descent from the South West of England.

They also carefully looked at a specific genetic variant associated with the nicotine receptor as it had previously been found to be associated with how much people smoke once they pick up the habit.

Some 47 percent of women with two copies of the non-addictive gene said they had stopped smoking in the final three months of pregnancy, compared with only 34 percent of women with two copies of the smoking addiction gene.

Expectant mothers are under considerable and social pressure to stop smoking but there are a number of factors that influence whether they quit, including age, education, and whether or not their partners smoke, researchers said.

Dr. Rachel Freathy, one of the researchers, said they were keen to investigate whether the genetic variant that influences increased cigarette consumption also had a role to play as an extra hurdle to quitting smoking during pregnancy.

“Our study suggests that it does,” she said.

“There are parallels with the obesity gene in that people think it’s matter of self control but it’s more complicated than that,” said Co-author Professor Tim Frayling, an expert in human genetics.

However, he added that it was clear that some women with two copies of the addictive gene could give up smoking.

“It just means it’s more difficult for some people than others.”

The same genetic variant may apply in people with Crohn’s disease, as they are also strongly advised to stop smoking in order to ease the symptoms of their condition.

While genes had been implicated in nicotine addiction, there are still many other factors that have an impact, including social circumstances, according to Dr. Alex Bobak, a GP in Wandsworth, south London.

He said experts could look into those sub-groups and see if they benefit more from certain kinds of treatment to help them kick the habit.

Additionally, NHS support is available for pregnant women who are able to take all forms of nicotine replacement therapy, he said.

The full study can be found in the journal Human Molecular Genetics.

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Human Molecular Genetics

Peninsula Medical School