Measurement of cervical length in pregnancy: comparison between vaginal ultrasonography and digital examination.

Evaluation of the gravid cervix uteri is an important part of prenatal care, especially in the patient at risk for preterm birth. Seeking a method of cervical length measurement that could be used easily regardless of patient habitus, location of the cervix, and gestational age, we used a vaginal probe with a 240 degrees scanning angle in gravidas at various gestational ages to test the theoretical advantages of the wide scanning angle. Among the first 201 examinations, cervical length was measured successfully in 99.5% of cases. This success rate compares favorably with those of abdominal sonography and vaginal sonography using the standard 90 degrees scanning angle sector probes. We also compared this method with digital examination in a double-blind fashion. Only a fair degree of association between sonographic cervical measurements and measurements obtained by digital examination was found, reflected in a correlation coefficient of 0.49.