Diagnostic ultrasound in the assessment of patients with incompetent cervix.

Twenty-five pregnant women with suspected cervical incompetence were assessed by serial ultrasound. A dilating internal os was documented in one patient, incompetence was ruled out in two, and a 'slipping suture' was demonstrated in another; the remaining patients were subjected to cerclage on the basis of their history alone. Patients in whom the diagnosis of cervical incompetence is indefinite should have a diagnostic ultrasound scan to visualize the cervix for length, opening of the canal and integrity of the internal os. Selective ultrasonography may be beneficial in both the diagnosis and treatment of cervical incompetence.