Women suffering from longCOVIDhave a greater risk1 of experiencing abnormal uterine bleeding. The symptoms of the illness intensify during the perimenstrual and proliferative phases of themenstrual cycle, notably fatigue, headaches, andmuscle pain. This bidirectional relationship between long COVID and menstrual disorders has been revealed by a French-British research team co-led by a CNRS researcher. An inflammatory reaction is suspected of being behind this connection, after the discovery of an immune cell cluster in the endometrium of the patients receiving treatment. No abnormalities were detected in relation to ovarian hormones. These conclusions, which were just published inNature Communications, are based on a combination of three approaches: a study conducted among 12,187 British women; follow-up care for 54 women suffering from long COVID for three months; and analysis of blood and endometrial samples. As long COVID affects 3-7% of the world’s population, and is twice as prevalent among women than men, this novel study paves the way for new therapeutic prospects. It also underscores the importance of considering the menstrual cycle in long COVID biomarkers, as well as the need to develop therapies specifically adapted to women. Maybin, J.A., Walker, C., Watters, M. et al. The potential bidirectional relationship between long COVID and menstruation. Nat Commun 16, 8187 (2025). https://doi.org/10.1038/s41467-025-62965-7