An IUD is not a contraindication  to using the abortion pills, but it does require some precaution. A pregnancy that occurs with an IUD in place increases the risk that it is an ectopic pregnancy (pregnancy not inside the uterus). Whenever possible, the safest recommendation to have the IUD removed prior to using the abortion pills.
 Ipas. (2019). Clinical Updates in Reproductive Health. L. Castleman & N. Kapp (Eds.). Chapel Hill, NC: Ipas. Retrieved from: https://ipas.azureedge.net/files/CURHE19-april-ClinicalUpdatesInReproductiveHealth.pdf