Take Norethindrone daily, at the same time of day. Like other progestin-only pills, Norethindrone does several different things to prevent pregnancy. It can stop ovulation in some women but this doesn’t happen 100% of the time, so the other ways are important too. Norethindrone makes the mucus in your cervix thicker, so it’s difficult for sperm to get through and fertilize an egg. Then, just in case, it also changes the lining of your uterus so that a fertilized egg can’t attach.