A study showing women with asthma are more likely to miscarry and have fertility problems highlights the need for good disease control in this group, researchers said.

The Danish team of researchers said the risk appeared higher in those with severe or uncontrolled disease.

Speaking at the European Respiratory Society annual Congress said team told delegates they had looked at data from 769,880 women born between 1976 and 1999.

Asthma was defined by medical records for repeated prescriptions for medication.

They found a higher rate of foetal loss in women with asthma at 17% compared with 15.7%.

And the likelihood of fertility treatment was also higher compared to women without asthma at 5.6% versus 5%.

Those whose asthma was the most severe and required treatment at step four to five of the international GINA guidelines had a 62% higher chance of having needed fertility treatment, they reported.

Women in the study with three or more prior asthma exacerbations had a 38% increased risk of needing fertility treatment, they added.

But overall the number of live births was the same in women with and without asthma which they said was reassuring.

Study leader Dr Anne Vejen Hansen from the department of respiratory medicine at Copenhagen University Hospital said: ‘Previous studies have shown that it takes women with asthma longer to get pregnant than those without asthma when undergoing fertility treatment, and that asthmatic women who succeed in getting pregnant have more often had fertility treatment than non-asthmatic women.

‘But most existing studies are on women who have actually got pregnant, so we wanted to examine fertility outcomes on a national scale, to also include those that might not become pregnant at all.

‘We found that women fulfilling the definition of asthma had a higher rate of foetal loss and an increased use of fertility treatment.’

She added: ‘The more severe the asthma and the more flare ups the women experienced, the more likely they were to need fertility treatment. Why this is, is not clear. It might be related to systemic inflammation throughout the body, including women’s reproductive organs.’

The team said they were now planning to look into possible effect of male asthma on fertility.

Professor Lena Uller, chair of the ERS group on Airway Pharmacology and Treatment and Head of the Respiratory Immunopharmacology research group at Lund University, Sweden, said it was reassuring that women seem to have the same live birth rate regardless of their asthma.

‘However, the results also indicate that women with asthma should take into consideration potential reproductive challenges in their family planning. If women with asthma are worried about their fertility, they should speak to their doctor.

‘The fact that the more severe the asthma, the more the problems with fertility, suggests that uncontrolled asthma is the problem and we should be helping women to get their asthma under control.’

A version of this article was first published by our sister title Pulse