Contraceptive ‘mini pill’ linked to asthma attacks in younger women (2025)

The progesterone-only contraceptive pill may be linked to a higher risk of potentially life-threatening asthma attacks in younger women, research has suggested.

Researchers from Imperial College London have found that women taking the so-called “mini pill” had a 39 per cent increased risk of asthma attacks compared with women who had never taken the contraceptive.

The mini-pill is a once-daily contraceptive pill taken by approximately 3.1 million women in Britain each year.

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The research could provide an answer as to why women have a higher rate of severe asthma compared with men, the researchers said.

Chloe Bloom, a clinical senior lecturer in respiratory epidemiology at the National Heart and Lung Institute, Imperial College London, and lead author of the study, said: “Asthma is common in women of reproductive age, many of whom are taking the pill.

“This study helps women and healthcare professionals make more informed decisions about which contraceptive pill might be best for them. The findings also add another piece to the puzzle of why women may be more likely to have severe asthma than men.”

They compared this data with 127,502 women with asthma who were not on the pill.

They also then examined asthma attacks recorded among the women between 2004 and 2020, and found that women under 35 had a 39 per cent increased risk of asthma attacks.

The team found no link with asthma for women who took the combined pill, which uses both oestrogen and progesterone.

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They found no link between older progesterone-only contraceptive users and the prevalence of asthma attacks. Women on the mini-pill who took fewer asthma treatments such as inhaled or oral steroids were found to have a 20 per cent increased risk of asthma attacks, they said.

Women with eosinophilic asthma, who have high levels of blood cells called eosinophils, which cause inflammation, had a 24 per cent increased risk of asthma attacks if they were taking the mini-pill, although this finding was not statistically significant.

While asthma is more prevalent among infant boys than girls, asthma becomes more severe among girls as they age. A 2023 report from Asthma and Lung UK, which funded the study, said that the rate of admissions to hospital for asthma were three times higher in women than men among those aged 20 to 50, with women experiencing more frequent and severe asthma attacks and a higher mortality rate from the condition.

Erika Kennington, from Asthma and Lung UK, said: “This study is an important first step for women with asthma to better understand what lifestyle risks could increase their likelihood of an asthma attack.

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“But much more research is needed to provide them with enough information to make more informed decisions on the best contraception choice for them. In the future, it would be beneficial for women to have the risk of an asthma attack considered alongside other health risks, such as heart disease and cancer.

“However, this research is still at too early a stage to change treatment decisions or prescribing guidelines and doesn’t provide enough evidence for a prescriber to suggest to someone that they change their contraception pill.

“Historically, little has been understood about why asthma is worse for women, because funding for lung health research is on life support. This research highlights yet again the need for urgent action to increase investment into lung research to give everyone fighting for breath improved treatment options and a better quality of life.”

Apostolos Bossios, head of the European Respiratory Society’s group on airway diseases, asthma, chronic obstructive pulmonary disease and chronic cough, said: “We need much more research to understand why asthma is worse for women than men so we can begin to reduce the risk. This major study in an important step towards that aim.”