Nosebleeds in pregnant women may be caused by progesterone and vitamin K deficiency. 1. Progesterone: Pregnant women will secrete a lot of progesterone when they are pregnant, which will lead to blood vessel expansion, congestion, and increase the blood supply of the body, and the thin wall of the blood vessels of the nasal mucosa, the blood vessels can’t withstand the pressure, and the symptom of nosebleed will appear. This is a normal phenomenon, if the bleeding is not big, usually do not need special treatment. 2. Lack of vitamin K: Vitamin K has the function of promoting blood clotting, when the lack of vitamin K will cause the reduction of prothrombinogen, which will lead to coagulation dysfunction, and the symptoms of nosebleed will appear. Severe vitamin K deficiency may also affect the development of vision and intelligence of the fetus. Pregnant women are advised to consume foods rich in vitamin K, such as spinach. Pregnant women are advised to go to the hospital for regular checkups. When pregnant women experience symptoms of nosebleeds, they should go to the hospital for examination and diagnosis in a timely manner.