Women with asthma may take longer to get pregnant, the results of a new study indicate.

Danish researchers analysed questionnaires that had been filled in by more than 15,000 adult female twins who were no older than 41.

The participants were asked a range of questions including ones relating to asthma and fertility. They were then divided into two main groups - those who had asthma and those who did not. These were then further divided into sub-groups based on whether they had been treated for their asthma or not.

All of the women were also asked whether they had children and/or if they had been trying to get pregnant for more than one year.

Among the women, almost 1,000 said they had a history of asthma.

The study found that 21% of those without asthma took longer than a year to get pregnant. However among those with asthma, this figure increased to 27%.

Furthermore, the risk of experiencing a delay in conceiving was even higher among those with untreated asthma (30.5%) compared to those who were receiving treatment for their asthma (23%).

The scientists also noted a particular trend in relation to age. Women with asthma who were over the age of 30 were even more likely to face a delay in becoming pregnant - 32% compared to 24% of women below the age of 30 with asthma.

However, despite these findings, the study found that overall, women with asthma eventually gave birth to the same number of children as women without the condition.

"Our results shed light on the complex interactions between fertility and asthma. Although we observed women with asthma experiencing longer waiting times to pregnancy, our findings suggest that if women take their medication and control their asthma, they can reduce this delay," explained the study's lead author, Dr Elisabeth Juul Gade.

She pointed out that as the negative effect of asthma on fertility appeared to be reduced by treatment, ‘we can assume that the systemic inflammation characterised by asthma may account for the effect on delaying fertility'

"Despite the delay, our overall results suggest that women with asthma had the same number of children, which is due to the fact that they tend to conceive at an earlier age compared to those without, getting a head start on their reproductive life," she added.

Details of these findings are published in the European Respiratory Journal.

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