A woman is 34 years old, it is her tenth labor at full term. It is known from the anamnesis that the labor started 11 hours ago, labor was active, painful contractions started after discharge of waters and became continuous. Suddenly the parturient got knife-like pain in the lower abdomen and labor activity stopped. Examination revealed positive symptoms of peritoneum irritation, ill-defined uterus outlines. Fetus was easily palpable, movable. Fetal heartbeats wasn't auscultable. What is the most probable diagnosis?