[Echographic detection of cervical incompetence. Comparison between the abdominal and perineal route]

Ultrasonographic measurements of the cervix in perineal and abdominal projections were compared in 61 women. Measured by the abdominal route the diameter of the internal os in most cases exceeded by 4 mm that measured by the perineal route, and cervical incompetence can be diagnosed when the internal os is equal or superior to 24 mm. For the abdominal measurement to be reliable the posterior vesical angle must be well marked, which means that the bladder must be moderately filled.