Infertility in women with asthma - does asthma also exist in the uterus?

Prolonged time to pregnancy, increased need for fertility treatment, and increased pregnancy loss have been reported in women with asthma. However, it is unknown whether uterine inflammatory cells negatively affects fertility in this group. We explored whether women with asthma undergoing fertility treatment have increased inflammatory cells in the endometrium compared to women without asthma. Thirty women with and without asthma (1:1) undergoing fertility treatment were included in this explorative observational study. Asthma was defined by symptoms and a positive bronchial challenge test. Participants underwent questionnaires, fractional exhaled nitric oxide measurement, blood sampling, spirometry, methacholine challenge, induced sputum, and 2/3D ultrasound scan of the uterus followed by endometrial biopsy near ovulation. Endometrial biopsies revealed no significant differences in inflammatory cell types between women with asthma versus women without asthma. Women with asthma had higher airway responsiveness, atopy, IgE, and eosinophil counts, as expected, but similar reproductive history and treatment characteristics. No differences were observed in plasma cells/mm2 (median(IQR) 0.15(0.14-0.65); 0.33(0.21-0.92), ns), mast cells/mm2 (median(IQR) 2.99(1.31-3.47); 3.72(3.25-9.57), ns) nor CD3⁺ or CD20⁺ lymphocytes or eosinophils. Biomarker analysis across tissues showed no significant association with asthma after multiple testing correction. This exploratory study found no evidence of differences in endometrial inflammatory cells between infertile women with and without asthma. However, the small sample size limits statistical power and a Type II error cannot be excluded.