When ostium uteri outspread to 3 cm , degree of pains in the ease pain group was higher than the control group in pregnant women P < 0.01 ;
产痛程度比较，宫口开大3cm时镇痛组高于对照组，均P<0.01，宫口近开全时镇痛组疼痛程度低于对照组，均P<0.01；
ostium uteri