Head basin disproportion

Introduction If the pelvic stenosis of the mother or the head of the fetus is too large, the birth can not pass through the birth canal; or the pelvis is normal, but because the head of the fetus is too large, it can not pass through the birth canal. This phenomenon is called "the head basin is not called."

Cause

The head basin does not mean that the fetal head is not commensurate with the size of the maternal pelvis. Whether the delivery process can be successfully completed depends on the three factors of productivity, birth canal and fetus. The three are coordinated without abnormalities and can be delivered vaginally. Otherwise, any one or more of the factors are abnormal or unable to adapt to each other. Obstruction can lead to dystocia, timely detection and treatment of dystocia, is the key to reducing the neonatal morbidity and mortality, so that the mother and baby turn to safety.

an examination

Related inspection

Pelvic measurement obstetric B-ultrasound

The pregnant woman emptied the bladder, lying on her back and straightening her legs. The examiner places his hand over the pubic symphysis and pushes the floating fetal head toward the pelvic cavity. If the fetal head is lower than the plane of the pubic symphysis, it means that the fetal head can enter the basin. The head basin is symmetrical, which is called the trans-shadow sign. If the fetal head and the pubic symphysis are in the same plane, it means that the suspicious head basin is not called. Positive; if the fetal head is higher than the pubic symphysis plane, it means that the head basin is obviously not called, which is called positive across the shame. For pregnant women with positive cross-symptoms, they should take the two-leg flexion semi-recumbent position and re-examine the fetal head cross-symptom sign. If it turns negative, it indicates that the pelvic inclination is abnormal, not the head basin. Relative to the head basin does not mean that the pelvis is normal, but the fetal head is not able to enter the basin due to the larger fetus.

Differential diagnosis

Common head basins are not called symptoms. The pelvic entrance plane is narrow and needs to be differentiated from the following symptoms.

(1) simple flat pelvis (simple flat pelvis): the entrance of the pelvis is flat and round, and the squat protrudes forward and downward, so that the anterior and posterior diameter of the pelvic entrance is shortened and the transverse diameter is normal.

(2) rickets flat pelvis: due to childhood rickets, bone softening caused the pelvis to deform, the sputum was pressed forward, the anterior and posterior diameter of the pelvic entrance was significantly shortened, the pelvic entrance was kidney-shaped, the lower part of the humerus moved backward, and the normal curvature of the humerus was lost. , straighten back to the back. The tailbone is hooked to the pelvic outlet plane. Due to the abduction of the humerus, the diameter of the iliac spine is equal to or greater than the intercondylar diameter; due to the valgus of the ischial tuberosity, the angle of the pubic arch is increased and the transverse diameter of the pelvic outlet is widened.

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