Australian researchers have found that short and long-term asthma treatments can have an effect on how quickly a woman becomes pregnant, with women who use short-acting asthma relievers taking longer to conceive.

Led by Dr. Luke Grzeskowiak from the Robinson Research Institute, University of Adelaide, Australia, the study looked at more than 5,000 women in Australia, New Zealand, the United Kingdom and Ireland who were expecting their first babies and in the early stages of pregnancy.

The women were asked if they had been diagnosed with asthma and, if so, which medicines they had used, as well as how long it had taken them to become pregnant.

The researchers found that more than 10 per cent of women in the study said they had asthma and, overall, these women took longer to get pregnant.

However, when researchers separated asthmatic participants according to the type of treatments they were using, they found that women who took long-acting asthma treatments conceived just as quickly as the women without asthma.

On the other hand, women using short-acting treatments took 20 per cent longer to conceive on average, and were 30 per cent more likely to have taken more than a year to conceive, which the researchers defined as the threshold for suffering infertility.

The findings still held true even after researchers took into account other factors known to influence fertility, such as age and weight.

Dr. Grzeskowiak now says the results are reassuring for women with asthma, who may be concerned that using inhaled corticosteroids could reduce fertility.

Professor Mina Gaga, president of the European Respiratory Society, also commented on the findings saying, "Asthma is a common condition but in the majority of cases it can be well-controlled with the right medicines. Women who are trying to conceive and women who are already pregnant are naturally concerned about the effects of their medicines, although there are large studies showing that asthma medications are safe, in fact safer than not taking medication."

"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."

Dr. Grzeskowiak also added that, "There is plenty of evidence that maternal asthma has a negative impact on the health of pregnant mothers and their babies, and so our general advice is that women should take steps to get their asthma under control before trying to conceive."