Incompetent Cervix: What Causes It, and How It's Treated

Medically Reviewed by Dr Sravya, MBBS, MS 


Still, many of us believe an incompetent cervix is a defect in women rather than a medical condition just like any other. Remember, it does not describe your body; if you are diagnosed with an incompetent cervix (also known as cervical insufficiency or a weak cervix), it is not your fault, nor could you have prevented it from happening. The cervix is the opening of the uterus that connects it to the vagina. Usually, the cervix will be closed and firm before pregnancy. When you get pregnant, and as the baby grows and reaches full term, the cervix will soften, get thinner (efface), and open up (dilate) for delivery. If you are diagnosed with an incompetent cervix, the cervix will begin to open soon, causing you to deliver early or leading to miscarriage. But still, with the condition, you can stop your baby from being born too early with medical help. Let’s see this article in detail about the symptoms, causes, diagnosis, and treatment of cervical insufficiency.

What is an incompetent cervix?

Incompetent cervix (cervical insufficiency or weak cervix) is a condition in which the cervix of a pregnant woman opens up too early or weakens or shortens in the second or early third trimester without any prior sign, leading to premature birth (baby born before 37 weeks of pregnancy) or late miscarriage (loss of pregnancy).

Various studies show that it is found in 1 in 100 pregnancies. It occurs commonly in the second trimester, that is, 14–27 weeks of pregnancy. It is still unclear what causes cervical insufficiency, so it is difficult to diagnose and treat. Perhaps researchers have found the risk factors that can lead to an incompetent cervix. 

Cervical insufficiency causes

What are the signs and symptoms of an incompetent cervix?

An incompetent cervix may show no noticeable changes. As it may not show symptoms in most cases, healthcare providers will tell you if you are at risk based on your past medical history. But some women start showing mild symptoms of cervical insufficiency at the beginning of the 14th week, up to 20 weeks.

Be cautious and look out for signs like:

Why do you have an incompetent cervix?

The exact cause of cervical insufficiency has not yet been identified. This occurs when your cervix is not strong enough to withstand the weight of a growing baby. You are at high risk and may develop an incompetent cervix.

How do you find out if you have an incompetent cervix?

Your healthcare provider can diagnose a weak cervix with the help of examinations of the pelvis and imaging techniques such as ultrasound or MRI. But no relevant test can be done before pregnancy to detect if you will have an incompetent cervix. An ultrasound or MRI can be done before pregnancy to find out if there are any uterine abnormalities or congenital problems.

A transvaginal ultrasound is usually done to diagnose an incompetent cervix. During this examination, a transducer ( thin, wand-like device) is placed inside the cervix. This transducer produces sound waves that get converted to images while scanning and shows them on a screen. This scanning will help to check the length of the cervix and if any tissues are sticking out of the cervix. 

The regular transvaginal ultrasound begins at 16 weeks. This will help you know if there are any changes in the length of your cervix and check for signs of early shortening of the cervix. If the cervix is shorter than 25mm, you will be at greater risk for cervical insufficiency.

In a pelvic examination, your physician will check if the amniotic sac, where the baby is growing, is felt through the cervical opening. If this amniotic sac wall is in the cervical canal or vaginal canal, it’s called the prolapsed fetal membrane. At this stage, your healthcare provider will ask you to watch out for any contractions.

Vaginal swabs: this is to detect any substance (fetal fibronectin) in the vagina that will only be present if you have an increased risk for early labor.

Lab tests will be requested to rule out infections. This will be done by taking samples of your amniotic fluid (amniocentesis).

How do you treat an incompetent or weak cervix?

The moment you are diagnosed, your healthcare providers will start various medications and treatments that will help you prevent premature delivery or miscarriage due to cervical insufficiency.

Cerclage (cervical stitch)

It’s one of the procedures done for cervical insufficiency to keep the cervix closed and hold the growing baby. Cerclage is extremely effective for prolonging pregnancy in women with cervical insufficiency. In this procedure, a band of strong thread is stitched around the cervix under spinal anesthesia. After the procedure, you will be asked to take rest and stop doing any physical activities. Cerclage procedures are typically done at around 12 to 14 weeks of pregnancy. At around 37 weeks of pregnancy, your healthcare provider will remove the stitches, so a vaginal delivery is possible for you.

Your healthcare provider may recommend a cerclage procedure for you if:

    1. You had cerclage in previous pregnancies.
    2. You have a medical history of miscarriages in the second trimester.

Your healthcare provider will not perform the cerclage procedure on you if you’re not the right candidate for it. It’s not done when

    1. pregnant and carrying more than one fetus, as it has a higher risk of preterm delivery.
    2. The cervix has dilated upto 4 centimeters 
    3. You have your amniotic membrane ruptured (water broke). 
    4. If you have no intraamniotic infections. 

In rare cases, some complications may occur associated with the cerclage procedure. This includes internal bleeding, infection, uterine rupture, or a tear or cuts in the cervix.


In cervical insufficiency, a weekly shot of progesterone from the 16th week to the 36th week will reduce the risk of preterm delivery. Instead, a daily dose of progesterone, which can be inserted in the vagina, can also help. This is advised for women with prior preterm births to reduce the recurrence. It is not always recommended for multiple pregnancies. 


If you’re having premature labor or you’re showing symptoms of it and there is a chance for survival for your baby, your healthcare provider will give you steroids. The chances of survival usually occur after 22 weeks. Steroids can stop preterm labor. It can also help your baby develop their lungs more quickly 


This is a device that fits inside the vagina and will help hold the uterus in place. More research is needed to find out if Pessary can be used to effectively treat an incompetent cervix.

Can you prevent an incompetent cervix?

You cannot prevent cervical insufficiency ( incompetent or weak cervix), but you can follow certain steps that will help you have a healthy pregnancy. Avoid substances like alcohol and drugs; take all the prenatal vitamins; attend all of your prenatal appointments and checkups; gain a healthy weight during pregnancy; and limit sexual activities or other physical activities.

If you had an incompetent cervix during pregnancy or had previous miscarriages, talk to your gynecologist if you’re planning to conceive again. Proper communication with your health provider and proper evaluation will help with early diagnosis and preventive measures.

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