What Can a Transvaginal Ultrasound Show?
During pregnancy a woman’s cervix is usually between 2.5 to 5 cms long (the average length is about 3 cms) and completely closed. As a woman gets closer to delivery, the cervix slowly undergoes two kinds of changes: The cervix shortens (called thinning or effacement). Effacement is measured in percentages from 0 (no effacement) to 100% (complete effacement). It begins in the upper part of the cervix (the part closest to the baby) and moves down toward the vagina. The cervix opens (called dilation). This is measured in centimeters from 0 (no dilation) to 10 cms (complete dilation). During a transvaginal ultrasound, your doctor will first check the length of the cervix: the shorter your cervix, the greater your risk for preterm labor. He’ll also look to see whether the membranes surrounding the baby (the bag of waters) have come down into the cervical opening (called funneling). Funneling can happen when the cervix starts to efface and the membranes begin to fall into the upper part of t
