Hi, Taking Regesterone (norethisterone) tablets can delay your menstrual cycle by preventing ovulation. However, it is important to note that missing a period is not always a reliable indicator of pregnancy, and there may be other reasons why your period is delayed. If you are concerned about the possibility of pregnancy, you can take a home pregnancy test to find out. It is best to wait until at least a week after your missed period to take the test for more accurate results. In addition, stress, changes in weight, and certain medical conditions can also affect your menstrual cycle. If you are experiencing other symptoms such as abdominal pain, nausea, or unusual vaginal discharge. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Diwashish Biswas, Internal Medicine Specialist