Third trimester of pregnancy see red whether serious to first understand the cause of the disease, may be a pre-eclampsia, fetal arrest, placenta hypoplasia state and other causes of see red, such as pre-eclampsia is relatively not so serious, fetal arrest is more serious. The third trimester of pregnancy has formed the placenta, the development of the fetus in the uterus is relatively stable, at this time there are doing strenuous exercise, sexual intercourse, etc., stimulate the uterus contraction may cause preeclampsia with red manifestations, the bleeding is relatively small, through the treatment of fetal preservation can be restored to normal, it is not serious. The third trimester of pregnancy may be red, but the embryo chromosomal abnormalities, maternal viral infections, endocrine disorders and other causes, the fetus in the uterus has ceased to develop, is more serious, has been diagnosed with the need for timely termination of pregnancy, such as uterine clearance. The third trimester of pregnancy may also be the placenta low state, the placenta is close to the cervical os, pregnant women with a large amount of activity or overwork, the cervical os will have a small peeling surface between the placenta and the uterine wall, which may cause bleeding, bleeding can be less successful in preserving the fetus, the occurrence of spontaneous abortion or bleeding is more serious. Redness in the third trimester of pregnancy is not normal, it is recommended to go to the hospital in time to check the cause of treatment.