1. Objective To study a better method of judging cephalopelvic disproportion on plane pelvic outlet.

2. Results Cephalopelvic disproportion, abnormal position of fetus, history of premature birth and abortion, inflammation of reproductive organs were the most factors of PROM.

3. B. Cephalopelvic disproportion is a disparity between the size of the maternal pelvis and the fetal head that precludes vaginal delivery. This condition can rarely be diagnosed in advance.

4. The cephalopelvic disproportion was the major indication in the spontaneous labour group.

5. The cesarean delivery rate more than doubles when passing the 42nd week compared with 40 weeks because of cephalopelvic disproportion resulting from larger infants and by fetal intolerance of labor.