A 24-year-old primipara was hospitalized with complaints of discharge of the amniotic waters. The uterus is tonic on palpation. The position of the fetus is longitudinal, it is pressed with the head to pelvic outlet. Palpitation of the fetus is rhythmical, 140 bpm, auscultated on the left below the navel. Internal examination: cervix of the uterus is 2,5 cm long, dense, the external opening is closed, light amniotic waters are discharged. Point out the correct component of the diagnosis: