Several disorders related to the placenta can occur. Its implantation can be abnormally low, even covering the internal os of the cervix (placenta previa), presenting a major risk for childbirth. History of uterine surgery including cesarean section, advanced maternal age, multiparity, or use of tobacco are all risk factors for placenta previa. The adhesion of the placenta can also be abnormally deep within the myometrium, being at risk for severe perinatal hemorrhage during delivery. In placenta accreta and increta, the invasion of the myometrium is not transmural, whereas placenta percreta invades the uterine serosa and possibly the neighboring organs. Placenta previa and history of cesarean section are the main risk factors. Ultrasound is the first-line examination with excellent performances. MRI is indicated in case of doubt or to plan the surgery. It should ideally be performed between 24 and 30 weeks of gestation and always with knowledge of clinical context and ultrasound findings. Gestational trophoblastic diseases can be benign (complete or partial hydatidiform mole) or malignant (invasive mole or choriocarcinoma). The MRI appearance of retained conception products can overlap with those of trophoblastic pathologies, with the HCG value being very high in the latter.