Thank you for asking on HealthcareMagic.com, providing better healthcare for you. If your blood work was done for qualitative hCG testing (a pregnancy test) then based on your result pregnancy is ruled out. A tubal ligation (known as having your tubes tied) is a type of permanent birth control. It s possible to reverse a tubal ligation, but reversal requires major surgery and isn t always effective. However, a tubal ligation doesn t affect your menstrual cycle. There are many factors that may cause missed periods, but finding the cause requires further evaluation and a consult with your gynecologist. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions. Wishing you good health.