Women are much more likely to become smokers if their mothers were stressed during pregnancy, the results of a new study indicate.

The findings also confirm that women are more likely to become dependent on nicotine if their mothers smoked during pregnancy.

It is already well-established that smoking while pregnant can increase the risk of a number of things, such as having a baby with a low birth weight and sudden infant death syndrome (cot death).

Despite this, many women continue to smoke during pregnancy. US researchers decided to look into the issue of nicotine dependency later in life among people born to women who smoked during pregnancy.

They used data from a large study that began in 1959 involving over 50,000 pregnant women. The children of these women were monitored for the next 40 years. The researchers also focused on over 1,000 mothers whose smoking status and hormone levels were measured during pregnancy. Their children were interviewed when they reached adulthood.

The study found that daughters who had been exposed to high levels of the stress hormone cortisol while in the womb, were much more likely to go on to become smokers. However, the same findings were not found in sons.

If a mother smoked during pregnancy, their daughters were also more likely to become smokers later in life.

"Our study suggests that maternal smoking and high stress hormones represent a 'double-hit' in terms of increasing an offspring's risk for nicotine addiction as an adult. Because mothers who smoke are often more stressed and living in adverse conditions, these findings represent a major public health concern," commented the study's main author, Dr Laura Stroud, of the Miriam Hospital in Rhode Island.

She said that the results highlight the ‘particular vulnerability of daughters', adding that it is unclear why these differences between daughters and sons exist.. However, she suggested that cortisol and nicotine ‘may affect developing male and female brains differently'.

She also warned that if daughters of smoking mothers are more likely to become smokers themselves, ‘the result is a dangerous cycle of intergenerational transmission of nicotine addiction'.

Details of these findings are published in the journal, Biological Psychiatry.

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