For some time, the hypothesis that the Covid-19 vaccines interfered with the female menstrual cycle, was dismissed as a Right-wing conspiracy theory. However, evidence is emerging that the Covid-19 vaccines do indeed impact upon the menstrual cycle, affecting the change in the length of the cycle, affecting the hypothalamic-pituitary-ovarian axis function. Individuals receiving two Covid-19 vaccine doses in a single cycle do appear to experience a longer, but temporary cycle length change, of about a day. That may not seem very dramatic, and in a sense, it is not, but is it first mainstream scientific evidence, and who knows what will come next?
https://news.yahoo.com/womens-periods-may-coronavirus-vaccination-131424573.html