Transvaginal ultrasonography in a pregnancy of a gestational age of 22 weeks, measuring the length of the cervix to rule out cervical incompetence. In this case, the cervical length is over 40 mm, which is normal. Part of the head of the child is visible at upper right. This measurement was not optimally performed, since it should be measured without any pressure on the cervix from the ultrasound transducer, so that there is only one measured distance instead of several fragmented ones.