Mechanism of Dystocia Due to Excessive Pelvic Inclination and Its Correction

Objective:To explore the clinical manifestation of excessive pelvic inclination and mechanism of its correction. Methods:①Pelvic inclination angles were measured with an inclinometer in 1000 singleton pregnant women,whose cephalopelvic score 8,occiput-anterior position, and with out malformation of pelvis and spine. The clinical menifestation was inspected throughout delivery. ②Variations of pelvic inclination were also inspected in 100 pregnant women from early pregnancy to antepartum,and to postpartum.Results:Excessive pelvic inclination means 53 degrees in inclinometer,synonymous with 68 degrees in radiographic measurement. Hs prevalence was 7.8%.The main manifestations included:pendulous abdomen,positive span-pubis sign,nonengagement of fetal head, and severe perineum laceration. Conclusions:Excessive pelvic inclination is caused by enlargement of lumber-sacral angle. Head pressure axis directing at pubic is not on the same line with the pelvic axis during delivery,which lead to nonengagement of fetal head. Lumber vertebrae bend will change from ventral to dorsal direction on cyst-lithotomy position,then pelvis move forward and upward with lumber-sacral joint as a pivot. Thus small lumber-sacral angle and excessive pelvic inclination are corrected,and trans-vaginal delivery rate and obstetric quality will also be improved.