Women using short-acting asthma inhalers took longer to become pregnant than women using long-acting inhaled asthma medications and those without asthma, researchers from the University of Adelaide in Australia, have found.

The study, published in the European Respiratory Journal, used data from the Screening for Pregnancy Endpoints (SCOPE) study, which included 5600 woman from Australia, New Zealand, the UK and Ireland. The women were all in the early stages of pregnancy with their first child.

Around 10 percent of participants in the study reported that they had asthma. Women treating their asthma with short-acting beta-agonists took on average 20 percent longer to conceive than women without asthma, or those using long-acting inhaled corticosteroids. Short-acting medication takers were also 30 percent more likely to take more than a year to conceive.

'Several studies have identified a link between asthma and female infertility, but the impact of asthma treatments on fertility has been unclear,' said Dr Luke Grzeskowiak from University of Adelaide who led the study.

Asthma is one of the most common conditions affecting women of reproductive age. Today, an estimated 5.4 million people in the UK are receiving asthma treatment, according to Asthma UK.

The relationship between asthma and fertility is not well understood. Both women and healthcare professionals have expressed concerns in the past about the safety of using medication to control asthma during pregnancy.

'This large study provides reassurance that using preventers, which include inhaled corticosteroids and long-acting bronchodilators, to prevent asthma symptoms helps asthmatic women be as fertile as non-asthmatic women, while intermittent treatment with short acting relievers is associated with reduced fertility,' said Professor Mina Gaga, president of the European Respiratory Society and medical director of the respiratory department of Athens Chest Hospital.

However, researchers have expressed concern about the interpretation of the results. Professor Kevin McConway, a statistician at the Open University who was not involved in the study, said in a statement: 'Though the researchers found that the women taking only short-term relievers were more likely to take over a year to get pregnant, this effect was not big enough to rule out the possibility that it was simply due to chance.'

Professor Tony Fox, a pharmaceutical medicine researcher at King's College London added: 'The investigators should consider whether patients using symptomatic short-acting bronchodilators are actually treating their asthma less well than those patients using inhaled corticosteroids to prevent asthma attacks from happening in the first place.'

Further studies are planned for women undergoing fertility treatments to see if improving asthma control is able to improve fertility outcomes. 

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Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.