If you become pregnant during the month while taking Fentanyl, the effect on the fetus in this case is not significant. If you want to continue the pregnancy, you must go to the hospital for the appropriate tests, because in this case it is often not a planned pregnancy, and you have to do the appropriate tests without a health check. The most important thing is to know if there is any virus that can cause fetal malformation, if not and if the size of the gestational sac matches the number of days of menopause by ultrasound, and if the germ or the primordial heartbeat appears in the corresponding week of pregnancy, it means that the embryo is developing well and the pregnancy can continue. If you do not want to continue the pregnancy, you can have an abortion, but you should do the appropriate tests before the abortion.