The cervix is the narrow lower end of the uterus – it's the opening to the womb, located between the top of the vagina and the bottom of the uterus. To keep your unborn baby safe and protected, the cervix remains firm, long, and closed during a normal pregnancy. (The mucus plug seals the cervical opening to prevent bacteria from entering the womb.) The cervix will begin to soften, efface (grow shorter), and dilate (open up) late in the third trimester, when your body gets ready for childbirth.
Unfortunately, in some cases, a woman's cervix opens up too early, before the onset of labor. This condition is called cervical insufficiency, or incompetent cervix, and it can put your developing baby's health at risk.
If you have an incompetent cervix, it may be due to your cervix being shorter than it should be, or due to a weakened cervix that's not as firm as it needs to be for a healthy pregnancy. As the weight of your expanding uterus places increasing pressure on your weak or shortened cervix, the cervix might start to grow shorter (efface) and open up (dilate) without any sign of contractions.
You may be at higher risk for an incompetent cervix if you've suffered cervical damage as a result of a previous childbirth, past abortion, D&C, or other surgical procedures. In addition, if you were exposed to the drug DES while you were in your mother's womb, you may also be at risk for this pregnancy complication.
With cervical insufficiency, you won't feel any discomfort or pain when your cervix opens. Very few people realize that they have this complication until they experience a miscarriage or premature baby.
Cervical insufficiency puts you at risk for a miscarriage in the second trimester, preterm labor and delivery, and a condition called premature rupture of the membranes (in which your bag of water breaks before 37 weeks pregnant, before the onset of labor contractions). This condition also puts you at high risk for early preterm delivery – giving birth before pregnancy week 32.
Screening and Diagnosis for Cervical Insufficiency
Despite the fact that cervical insufficiency has been recognized in the medical community for many years, healthcare providers do not have a reliable method of screening for the condition. In the past, women rarely knew that they had a weakened cervix until they miscarried or suffered a related pregnancy complication. Nowadays, your doctor can use a transvaginal ultrasound to evaluate the length of your cervix and other cervical characteristics to detect cervical incompetence.
If you are diagnosed with a short or weakened cervix, your healthcare provider may recommend weekly ultrasounds to monitor the cervix for any changes, such as sudden shorten or dilation. This may signal a miscarriage or preterm birth. Though there is much research in this area, doctors don't have a 100 percent foolproof way to prevent miscarriage or preterm birth due to cervical insufficiency.
Some doctors may recommend pelvic rest (no sexual intercourse) and bed rest to help ward off premature labor. Some doctors may also suggest that you undergo a surgical procedure called a cerclage – which involves your physician suturing your cervix shut. The suture, or medical "stitch," will prevent your cervix from opening too soon. When it's time for your baby to be born, the suture will be taken out.
The success of a cerclage is controversial. Some studies have found the procedure is successful in delaying preterm birth, but others have found it ineffective. However, new research suggests supplementing a cerclage with progesterone injections may help reduce the risk of preterm birth in pregnant women with a weakened or short cervix.
Unfortunately, once your diagnosed with cervical insufficiency, you will experience the same problems in future pregnancies. That's why it's important for women with this condition to discuss any painful contractions, leakage, menstrual cramping, or pelvic pressure with your doctor as soon as possible.
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