Value of ultrasound in patients with cervical incompetence.

The diameter of the internal cervical os was measured before and after cerclage in twenty-eight pregnant women diagnosed as having cervical incompetence on the basis of previous obstetric history. At about the same gestational ages, measurements were taken in twenty-eight pregnant women with no obstetric complications and used as matched controls. There was a significant difference between the mean diameter of the os before and after cerclage in the study group (P less than 0.001). There was also a significant difference in the cervical os diameter, both before and after cerclage, when the study group was compared with the controls (P less than 0.001). Twenty-five per cent of the patients in the study group, however, had measurements that fell within the normal range. This study highlights the value of ultrasound in the selection of patients at risk and also in eliminating unnecessary operative procedures.