Sonographic assessment of the cervix in pregnancy.

Recent studies using transvaginal and transperineal sonography to monitor the cervix have dramatically increased our knowledge of morphological changes of the cervix throughout pregnancy. Knowledge of the normal and abnormal appearance of the cervix gives insight into the processes of premature labor and cervical incompetence. The finding of a short cervix can be used to identify (and possibly treat) patients at risk for premature delivery. This article reviews the use of cervical sonography in obstetric care, including the diagnosis of incompetent cervix, the detection and monitoring of premature labor, and the evaluation of placenta previa.