Asthma increases the time it takes for a woman to get pregnant, a study has shown.
The risk of delay is greater in women over the age of 30, and whose condition is untreated.
Researchers studied data on 15,000 female twins from Denmark with an average age of 27. All were asked if they had tried to get pregnant for more than a year without success.
Twins were used to take account of genetic and lifestyle factors that might affect pregnancy. A total of 995 participants had a history of asthma. Of this group, 27% experienced delayed pregnancy compared with 21.6% of non-asthma sufferers, a significant difference.
Undergoing asthma treatment reduced the chances of waiting for pregnancy to 23.8% compared with 30.5% for women not receiving treatment.