While it is not a common complication of pregnancy, some women may have an incompetent cervix. Occurring in 1 out of every 100 pregnancies, about 25% of second trimester miscarriages are caused by incompetent cervix.
What is an Incompetent Cervix?
Normally, during pregnancy, the cervix remains closed until you go into labor. At that point, the cervix begins to dilate in order to allow your baby to pass through the birth canal and be delivered. In women who have an incompetent cervix, though, the cervix is unable to remain closed for the entire nine months.
As your baby grows, increased amounts of pressure are placed onto your cervix. In women with an incompetent cervix, the additional pressure causes the cervix to slowly begin dilating at about the 13th week of pregnancy, just as you are finishing your first trimester. This gradual thinning and widening of the cervix occurs without any contractions or labor, though, so you are often not aware that it is happening. While your cervix weakens, the amniotic membranes that surround your baby begin to protrude down into the cervical opening. Eventually, the membranes will break, causing either a miscarriage, stillbirth or a premature birth.
Causes for an Incompetent Cervix
Women who have one or more of the factors below are at an increased risk of having an incompetent cervix:
- Previous cervical surgery
- DES exposure
- Trauma or damage to the cervix (maybe caused by a previous difficult birth or a D&C)
- Abnormally shaped uterus or cervix (congenital defect)
Getting a Diagnosis
Since there are often no physical signs of an incompetent cervix, it is not always possible to have the problem diagnosed before a miscarriage occurs. However, women who have had multiple miscarriages in their second or third trimester or who suspect they may be at risk are more likely to have their health care provider monitor them for a weakened cervix.
Determining whether a woman has an incompetent cervix is fairly simply. Incompetent cervix can be detected either through a manual pelvic exam or through an ultrasound. An ultrasound can measure both the opening and length of your cervix, while a pelvic exam will determine whether your cervix is dilating. However, your cervix may begin to dilate prematurely for reasons other than an incompetent cervix. Therefore, if it is found that your cervix is beginning to open, your past history of miscarriages will also be taken into account.
Incompetent cervix can be treated through a procedure known as cervical cerclage. This simple treatment involves sewing up your cervix with stitches. A cerclage will help to reinforce your cervix, allowing you to continue your pregnancy to term.
Cerclage is usually done between 14 and 16 weeks of pregnancy. In order for you to be able to give birth, though, those stitches will obviously need to come out. Cervical cerclage sutures are typically removed between 36 and 38 weeks pregnant. Although the initial procedure is done under some type of anesthetic, either local or general, and may require an overnight hospital stay, removing the cerclage stitches can be done in your doctor’s office and shouldn’t be too painful.
Once your sutures are removed, it shouldn’t be a problem to give birth vaginally. And don’t worry, you will not automatically go into labor just because your cervix is no longer reinforced with stitches.
Cervical Cerclage Risks
While cerclage is a very helpful procedure, with 80% to 90% of women going on to give birth to healthy babies, it is associated with some risks. These risks include:
- Rupture of the uterus or bladder
- Maternal hemorrhage
- Cervical laceration
- Preterm labor
- Premature rupture of the membranes
However, it is important to remember that these complications are rare.
Can Every Woman Have a Cerclage?
Not all women will be able to be treated for their incompetent cervix. Women who are affected by any of the following conditions will not be able to have a cervical cerclage.
- Cervix is dilated 4cm or more
- Cervix is irritated
- The amniotic membranes have ruptured and water has broken
- The baby has already died