7.1. General considerations. Classification
General considerations. Abnormal labor is a quite common complication. Its rate is 10-15% of the total number of childbirths.
Abnormal labor is characterized by abnormal uterine contractions that result in disordered physiology of the lower segment formation, abnormal mechanism of cervical dilatation (not due to distension but through tissue rupture). If uterine contractile activity (UCA) is disordered, we often note deviations in the delivery biomechanism, difficulty in fetal advancement, too slow, or on the contrary, too rapid - precipitated labor. Both these clinical scenarios are often accompanied by fetal hypoxia, lacerations of the birth canal, and hypotonic uterine bleeding. Every third cesarean section after the onset of labor is performed due to abnormal labor. Until now there are no reliable and completely harmless ways to prevent and correct impairments of UCA. This abnormality requires differential and early diagnostics of uterine contraction disorders. Consequences of misdiagnosis and inadequate treatment can be quite dangerous for mother and fetus. Attempts at artificial dilatation, distension, and dissection of the uterine cervix for labor acceleration and to overcome the resistance of rigid tissues did not produce expected results.
The main criterion for abnormal labor is basal uterine tone, which determines the main parameters of contractions and bearing down: the frequency and strength (amplitude), duration of a contraction, relaxation, and the pause between contractions, intraamniotic and intramyometric pressure which determine the processes of cervical dilation, and fetal advancement along the birth canal.
As a result, all forms of UCA disorders are divided into hypertonic and hypotonic dysfunction. Their common parameters are low efficiency of labor, impairment of uterine contraction physiology, and various complications for mother and fetus.