NORMAL CERVIX

Posterior to the angle of the urinary bladder. This relationship is constant because the cervix is fixed by parametrium at the posterior angle of the bladder. Endocervical canal is an echogenic stripe surrounded by hypoechoic fibrous stroma. Length is measured from internal os to its most caudal aspect in the fornix of the vagina.

• Internal os is the fibromuscular junction between the corpus uteri and the cervix. Sonographically they have a similar appearance and cannot be reliable differentiated. It can be localized by its interface with the lower amniotic cavity on longitudinal scans. The amniotic fluid typically is funnel shaped (apex of funnel forms an acute angle at the internal os).
• Normal Length.
• Transabdominal scan = 3.5-5cm. Variation due to compression from a full bladder.
• Transvaginal scan = 4.0-4.5cm.