A new study published in theEuropean Respiratory Journalshowed that there is no connection between combination oral contraceptives (COCs) and asthma in women of reproductive age. However, in some subgroups, progestogen-only pills (POPs) may raise the risk of asthma episodes. Female sex hormones have been linked to these variations, albeit the precise processes are unknown. Hospitalization, exacerbations of asthma, and a reduction in lung function are all linked to menstrual-related alterations. On the other hand, studies found hormone replacement treatment is linked to a higher incidence of asthma and the usage of asthma drugs in postmenopausal women. The effect of hormonal contraceptive usage on asthma risk has been the subject of very few investigations. A higher risk of asthma, wheezing, and other allergies, including hay fever, has been noted in some studies, while others have shown no correlation between the use of either hormonal contraceptives or combination oral contraceptives and asthma or asthma symptoms. In light of this ambiguity, this study looked in to the connection between women of reproductive age's asthma and their current usage of OCP. This research compared OCP never-users to new users using a combination oral contraceptive (COC) cohort and a progestogen-only (POP) cohort of women with asthma (18–50 years old) using the UK's Clinical Practice Research Datalink, which is connected to hospital admission and mortality data, 2004–2020. This study used Cox proportional hazards and inverse-probability of treatment weighting, taking into consideration comorbidities, asthma severity/control, and demographics. Age, BMI, blood eosinophils (x109 cells·L−1, normal <0.3, eosinophilia ≥0.3), and corticosteroid usage (lower use: ≤3 inhaled corticosteroid prescriptions, greater use: ≥4 inhaled and/or oral corticosteroids) were also classified by possible modifiers. This study shortlisted 1,29,151 and 1,32,676 for the POP and COC cohorts, respectively. Neither POP nor COC were linked to asthma episodes (weighted HR, 95% CI: POP=1.11, 0.97–1.28; COC=1.00, 0.89–1.13). Once asthma severity/control, demographics, and comorbidities were taken into consideration, the POP relationship was altered by asthma phenotype and corticosteroid usage but not by BMI. Asthma episodes were more likely to occur among POP users who were younger than 35 (1.39, 1.12–1.72), had eosinophilia (1.24, 0.97–1.58), or used less corticosteroids (1.20, 1.03–1.40). Overall, in women with eosinophilic asthma, younger women and women who take corticosteroids less often, starting exogenous progesterone without an estrogen component (POP) was linked to an increase in asthma episodes. Lee, B., Amir Reza, R. F., Wong, E., Tan, T., & Bloom, C. I. (2025). Oral contraceptives and the risk of asthma attacks: a population-based cohort study. ERJ Open Research, 01278–02024.https://doi.org/10.1183/23120541.01278-2024