Transvaginal and transabdominal ultrasonography of the uterine cervix during pregnancy.

Transvaginal and transabdominal ultrasound evaluation of the uterine cervix were compared in a study of 186 pregnant women. An empty bladder made transabdominal ultrasound measurement of the cervix more difficult, while bladder filling resulted in significant lengthening of the transabdominal cervical measurement. In contrast, transvaginal ultrasound cervical measurement was possible in all but 1 patient. Normal transvaginal ultrasound cervical measurements were significantly shorter on average than transabdominal cervical measurements, but compared closely with prior transabdominal ultrasound studies in which bladder filling was carefully controlled. Significant cervical shortening was not noted in most patients with a clinical diagnosis of incompetent cervix.