Hi, Microgestin is a combination birth control pill that contains ethinyl estradiol and norethindrone, which work to prevent ovulation, thicken cervical mucus to block sperm, and thin uterus lining to avoid fertilized egg implantation. Some common side effects of Microgestin may include nausea, vomiting, bloating, breast tenderness, headache, mood changes, changes in appetite or weight, and irregular or lighter periods. In your case, it is not uncommon for women to experience lighter periods while taking hormonal birth control, as the thinning of the uterine lining can reduce the amount of blood flow during menstruation. However, if you are concerned or experiencing any unusual symptoms, it is always best to speak with your healthcare provider to discuss your specific situation and determine if any further action is needed. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician