During the dynamic observation of a parturient woman in the second stage of labor it was registered that the fetal heart rate decreased to 90-100/min, and did not normalize after contractions. Vaginal examination revealed the complete cervical dilatation, the fetal head filling the entire posterior surface of the pubic symphysis and sacral hollow; the sagittal suture was in the anteroposterior diameter of the pelvic outlet, the posterior fontanelle was in front under the pubic arch. What plan for further labour management should be recommended?