The hazards of taking birth control pills when pregnant are as follows: First, it may cause unnecessary damage to the female uterus, and can also cause inflammation of the uterus, cervicitis, salpingitis and other parts of the fallopian tubes. Second, it will cause some damage to the female vagina, some contraceptive pills are placed into the vagina to play the purpose of contraception, in the process the drug will cause damage to the female vagina, may also cause vaginitis, and even cause inflammation of the fallopian tubes and so on. Thirdly, if you take birth control pills for a long time or frequently, it may lead to irregular menstruation, resulting in ovulation disorders, which may lead to non-pregnancy. Fourth, some birth control pills may cause nausea, vomiting, anorexia and a series of digestive problems. Fifth, contraceptive pills have a certain residual period, which may have adverse effects on the fetus in the future.