Blood in the toilet at 20 weeks of pregnancy may be a manifestation caused by various pathogenic factors such as preterm labor, urinary system diseases, intestinal and anal diseases. 1. Preterm labor with precursor: In the 20th week of pregnancy, pregnant women are stimulated by various pathogenic factors, which may cause obvious uterine contractions, inducing preterm labor with precursor, and the increase in abdominal pressure when going to the toilet may cause vaginal bleeding. 2. Urological diseases: If a pregnant woman is 20 weeks pregnant, there are various organic diseases such as urinary tract infections, urinary stones, etc., and the local tissues of the lesions ooze blood, there may be blood in the urine when going to the toilet to urinate. 3. Intestinal and anal diseases: 20 weeks pregnant, if the pregnant woman appears severe enteritis, ulcerative colitis, intestinal polyps, intestinal cancer, hemorrhoids and other organic diseases, may cause when going to the toilet to defecate, there is blood in the stool. Blood in the toilet in 20 weeks of pregnancy requires the pregnant woman to seek timely medical attention.