Over more than 100 years, fewer than 40 cases of decidual cast shedding — during which the uterus’ thick mucous lining is shed, intact — have been reported. But over a 7.5 month period in 2021, 292 women experienced it, raising questions about whether Covid-19 vaccines could be to blame.Decidual cast shedding – clinically known as membranous dysmenorrhea – is so rare that most people have never heard of it, including most health care workers.[i] It describes a gynaecological event during which the decidua, or the thick mucous membrane that lines the uterus, is shed in full, intact form.The “cast”...