If you are breast-feeding, have irregular periods or haven't been consistently using birth control, you may need to take a pregnancy test before Mirena is inserted or have it inserted during a period. If you have Mirena inserted more than seven days after the start of your period, you should be prepared to use backup contraception for one week. Taking a nonsteroidal anti-inflammatory drug, such as ibuprofen (Advil, Motrin IB, others), one to two hours before the procedure can help reduce cramping.