北京安太专家陈凤林教授指出：B超在怀孕前很难看出宫颈机能不全，除非是特别严重的，怀孕后，大部分人可以通过B超评估是否有宫颈机能不全，但小部分患者也是无征兆的。

Beijingan expert Professor Chenfenglin pointed out: B Super is difficult to see cervical insufficiency before pregnancy, unless it is particularly serious. After pregnancy, most people can assess whether there is cervical insufficiency through B Super. However, a small number of patients are also without warning.

正常情况下宫颈管正常长度为2.5-3cm,当做妇科检查时，宫颈内口能顺利通过7号扩宫棒，或妊娠期无明显腹痛而B超测内口宽度>0.5cm,宫颈管长度<2.5cm,有助于宫颈松弛流产的诊断。

Under normal circumstances, the normal length of the cervical tube is 2.5-3cm. When used as a gynecological examination, the cervix can successfully pass through the No. 7 dilation stick, or there is no obvious abdominal pain during pregnancy and the width of the B supermeasured inner mouth is & GT; 0.5 cm, cervical tube length & lt; 2.5 cm, helpful for the diagnosis of cervical relaxation abortion.