Asthma linked to recurrent pregnancy loss

Asthma — especially early-onset and uncontrolled asthma — appeared significantly associated with recurrent pregnancy loss, according to a study published in The Journal of Allergy and Clinical Immunology: In Practice.

Low-grade inflammation could be a common path for asthma and these losses, Casper Tidemandsen, MD, PhD, of the department of respiratory medicine at Copenhagen University Hospital-Hvidovre in Copenhagen, Denmark, and colleagues wrote in the study.

The researchers used national health registers to examine the records of 1.3 million women in Denmark. Of them, 128,553 women aged 6 to 45 years had filled at least two prescriptions for anti-asthma drugs within 12 months between 1977 and 2019.

Compared with the women without asthma, women with asthma had higher odds of having one pregnancy loss (adjusted OR = 1.05; 95% CI, 1.03-1.07), two pregnancy losses (aOR =1.09; 95% CI, 1.05-1.13), three or more losses (aOR = 1.18; 95% CI, 1.11-1.24) and recurrent pregnancy loss (RPL; aOR = 1.19; 95% CI, 1.12-1.27).

Women with early-onset asthma, defined as onset between ages 6 and 15 years, had an aOR of 1.47 (95% CI, 1.24-1.72) for three or more pregnancy losses.

Additionally, women with uncontrolled asthma — based on their use of 400 doses of short-acting beta agonists (SABA) or more per year — had an aOR of 1.6 (95% CI, 1.16-2.16) for three or more pregnancy losses compared with women with controlled asthma.

According to the researchers, women with asthma had significantly increased odds for all pregnancy loss outcomes, except for two or more pregnancy losses during the second trimester and stillbirth.

Outside of pregnancy loss, women with asthma also had higher odds of complicated delivery following RPL (aOR = 1.43; 95% CI, 1.17-1.74) compared with women without asthma.

This association between asthma, especially from an early age, and number of pregnancy losses was unidirectional, the researchers found.

Often, early-onset asthma is associated with a specific phenotype of asthma and Type 2 inflammation, typically characterized by eosinophilic inflammation, which could be more closely related with pregnancy losses, the researchers continued.

Women who experienced asthma onset before their first pregnancy saw a stronger association with three or more pregnancy losses than women who developed asthma after their first pregnancy, suggesting that the asthma itself or a shared immunological background could be driving the asthma.

The study further found that 28.3% of women with asthma and 36.7% of women without asthma never achieved a pregnancy (aOR = 0.93; 95% CI, 0.92-0.94).

However, the researchers cautioned that the population included women with infertility, chronic diseases making pregnancy impossible and women who had actively decided not to have children, making conclusions difficult.

Still, the researchers said the strongest associations between asthma and pregnancy losses occurred among women with a higher likelihood of an immunological background, suggesting the need for future studies to identify the mechanisms behind this relationship.

The researchers also noted the need to control asthma before and during pregnancy among women of childbearing potential, with particularly close monitoring of women with asthma and RPL during delivery.