A 38-year-old woman, para 3, has a history of 5 artificial abortions. Five minutes after giving birth, she started bleeding from her genital tracts (350 mL). The patient’s condition is satisfactory, her pulse is 92/min., blood pressure is 100/60 mm Hg. There are no signs of placental expulsion, its manual removal has to be performed. In some spots the placenta is somewhat difficult to detach. Make the right diagnosis: