The causes of bleeding after taking norethindrone for intercourse include drug reduction or missed doses. Norethindrone is a kind of short-acting contraceptive pill, which needs to be taken continuously and on time under the guidance of a doctor in order to achieve effective contraception. However, when the dosage of the pill is reduced or the dose is missed, it may cause irregular vaginal bleeding, which may also be manifested as bleeding after intercourse during the pill. A small amount of bleeding can be observed, but if the bleeding is heavy, it is necessary to follow the doctor’s advice to take additional estrogen until the drug is discontinued. Contraindications such as liver and kidney insufficiency should be ruled out before taking short-acting contraceptives, and side effects such as nausea, vomiting and amenorrhea may occur after taking the pill. If a dose is missed during the course of the pill, it should be replaced as soon as possible within 24 hours, and the possibility of contraceptive failure should be guarded against. Long-term use of the drug is not recommended for women at risk of cardiovascular disease. Bleeding after coitus with norethindrone requires hospitalization and symptomatic treatment under the guidance of a doctor.