When you are 37 weeks pregnant and there is yellow fluid running from the sheets, it could be a vaginal infection, but it could also be a precursor to labor. After a girl becomes pregnant, her vaginal discharge will increase significantly due to the higher level of estrogen in her body. However, normal discharge should be white or clear. 1. 37 weeks pregnant, there is yellow liquid flowing from the bed sheet, if there is obvious fishy odor, it may be bacterial vaginosis. Because of the increase in vaginal discharge, if you usually do not pay attention to the hygiene of the vulva, it may lead to bacterial vaginosis. With bacterial vaginosis, the leukorrhea has a fishy smell and is grayish-yellow in color, and occasionally symptoms of vulvar itching may occur. 2. If there is yellow fluid coming out of the vagina with some blood mixed in, this situation may be that labor is about to start. In the 24 to 48 hours before labor is initiated, due to the separation of the fetal membranes near the endocervical opening and the uterine wall, resulting in the rupture of capillaries, which will cause a small amount of bleeding, and then mixed with the cervical canal mucus to be discharged, which is commonly known as the red color. It is recommended to consult a doctor promptly if there are any uncomfortable symptoms during pregnancy, so that a clear diagnosis can be made and dealt with.