Hi, Birth control pills contains either estrogen and progesterone or progesterone only that is used to prevent unwanted pregnancies from unprotected sexual intercourses. It may cause irregular or abnormal uterine bleeding such as prolonged or short duration and heavy or scanty bleeding. Again, it can cause breakthrough bleeding or spotting between periods. Other side effects are nausea, vomiting, abdominal pain, bloating, indigestion, GIT upset, headache, dizziness, sweating, changes in body weight, vaginal discharge, vaginal bleeding, easily bruising or bleeding, changes in appetite, fatigue, tiredness, weakness, delayed wound healing, facial hair growth, acnes, changes in sleep pattern, breast tenderness and enlargement, dry mouth, changes in sex drive, allergic reactions etc. If any of these side effects persists for long or bother you, then you should consult your doctor promptly for medical attention. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Zubayer Alam, General And Family Physician