Radiologic appearance of the upper cervical canal in women with a history of premature delivery. II. Relationship to clinical presentation and to tests of cervical compliance.

Two hundred twelve women with histories of spontaneous second-trimester abortions or early preterm births (less than 34 weeks) were evaluated with hysterography in the nonpregnant state. The canal:cannula (C:CN) ratio, a representation of the width of the upper cervical canal, was related to the clinical characterization of the early delivery. Narrow canals were associated with bleeding or premature rupture of the membranes (PROM) preceding preterm labor. Wide canals were found in association with the clinical diagnosis of cervical incompetence. Those patients in whom preterm labor occurred in the absence of preceding bleeding or PROM had intermediate values. The results of two tests of cervical compliance, Hegar dilator passage and catheter balloon traction, were concordant and varied with the C:CN ratio.