9.1. Definition. Characteristics. Classification
Contracted pelvis has always been considered a difficult section of obstetrics since it requires an accurate assessment of its proportionality with the fetus is needed, knowledge of the peculiarities of labor biomechanism depending on the form of contraction, the obstetrician's endurance during delivery management, combined with the ability to timely identify the danger to the mother and fetus. Contracted pelvis is one of the causes of perinatal morbidity and mortality, maternal injuries.
Previously, experts said: "Forceps for contracted pelvis are like a fist for the eye?; "Look how the doctor manages delivery in contracted pelvis and you'll say if he is a good obstetrician.'' However, time has changed, and if there is disproportion between the size of maternal pelvis and the fetal head of significant degree, obstetricians prefer delivery by cesarean section. And if a degree of disproportion is insignificant? Anatomic contraction of the pelvis is not always an obstacle in delivery. In case of large size of the fetal head or its deflexion, asynclitism, the pelvis can be contracted even with its normal size.
Specific features of contracted pelvis in modern obstetrics. In modern obstetrics, we almost never encounter cases of grossly deformed pelvis nor its contraction of high degree. The prevailing cases are so-called "obscure", abnormal forms of contracted pelvis, which seem to be proper in size, but turn out to be contracted in delivery.
As a rule, the mechanism of delivery with these forms of pelvis is changed. The fetal head is engaged for a long time into the inlet plane of the lesser pelvis in the anteroposterior or transverse diameter but not in the oblique diam-