Diagnosis

An incompetent cervix can only be detected during pregnancy. Even then diagnosis can be difficult — particularly during a first pregnancy.

Your doctor will ask about any symptoms you're having and your medical history. Be sure to let your doctor know if you've had a pregnancy loss during the second trimester or if you had a procedure on your cervix.

Your doctor might diagnose an incompetent cervix if you have:

• A history of painless cervical dilation and second trimester deliveries
• Advanced cervical dilation and effacement before week 24 of pregnancy without painful contractions, vaginal bleeding, water breaking (ruptured membranes) or infection

Tests and procedures to help diagnose an incompetent cervix during the second trimester include:

• Transvaginal ultrasound. Your doctor may use transvaginal ultrasound to evaluate the length of your cervix and to check if membranes are protruding through the cervix. During this type of ultrasound, a slender transducer is placed in your vagina to send out sound waves that generate images on a monitor.
• Pelvic exam. Your doctor will examine your cervix to see if the amniotic sac has begun to protrude through the opening (prolapsed fetal membranes). If the fetal membranes are in your cervical canal or vagina, this indicates cervical insufficiency. Your doctor will also check for contractions and, if necessary, monitor them.
• Lab tests. If fetal membranes are visible and an ultrasound shows signs of inflammation but you don't have symptoms of an infection, your doctor might test a sample of amniotic fluid (amniocentesis) to diagnose or rule out an infection of the amniotic sac and fluid (chorioamnionitis).

There aren't any tests that can be done before pregnancy to reliably predict an incompetent cervix. However, certain tests done before pregnancy, such as an MRI or an ultrasound, can help detect uterine abnormalities that might cause an incompetent cervix.