A 14-year-old girl came to a general practitioner with complaints of weakness, loss of appetite, headache, rapid fatigability. Her last menstruation was profuse and lasted for 14 days after the previous delay of 2 months. Objectively, her skin is pale, heart rate is 90/min., BP is 110/70 mm Hg, Hb is 88 g/L. Rectal examination: the uterus and its appendages are without changes, no discharge from the genital tracts. What complication occurred in the patient?