Does The Length Of The Cervix Affect A Healthy Pregnancy ?

Your cervix is a tube-like structure that connects your uterus to the vagina. Cervical length is the length of this tube and the cervical opening.

Your reproductive system is created in such a way that it can hold the baby for 9 long months until the time of labor and delivery arrives. However, due to certain anomalies in the anatomy, the process of pregnancy and delivery could become difficult.


A shorter cervical length increases the risk of preterm labor and premature birth, which is likely to affect the newborn’s health.

How Does Cervix Change During Pregnancy?

Before the pregnancy, the cervix remains closed and rigid—wide enough to let the menstrual blood and sperm to pass through. When a woman becomes pregnant, the cervix gets sealed by the mucous plug—it protects the baby by preventing microbes from entering the uterus.


As the pregnancy progresses, the cervix gradually softens, decreases in length and starts to dilate to allow the baby to pass from uterus to the vagina when the labor begins. This is referred to as effacing and dilating. If the cervix starts opening or dilating before time, it poses a risk to the baby.

Why Causes Short Cervical Length?

Below are the factors which can influence the cervical length.


1. In the first trimester, the cervical length is determined by the mother’s anatomy—whether she has a small cervix from the beginning.

2. An infection in the cervix can also affect its length.


3. A distended uterus, which is when the uterus stretches too far, can also cause the cervical length to shorten. This is more common in moms with multiple pregnancies.

4. Inflammation of the uterine lining can affect the cervical length too.


5. If the mother has undergone an abortion or a cervical surgery, the cervical length might decrease.

6. If the complications arise due to which the mother bleeds during pregnancy, it can irritate the cervix and affect the cervical length.


7. An incompetent cervical tissue is when the cervical tissue is weak and causes loss of a healthy pregnancy, which can influence the cervix length.

How Is Cervical Length Determined?

Cervical length is determined using a transvaginal scan (TVS), which is done by inserting a transducer inside the vagina. The cervix is a tube-like structure and has an opening into the vagina, which is called external OS. The end that opens into the uterus is called internal OS. The TVS measures the opening from the internal OS to external OS in centimeters or millimeters.


By the time, the pregnancy reaches the 24th week of pregnancy, the cervical length is about 35 to 48 millimeters. The cervical length is termed as short if it is less than 25 millimeters before the 24th-week.  The risk of premature delivery is higher if the cervical length is found to be less than 20 millimeters.

The TVS scan is not a part of routine checkup during pregnancy. However, it is performed on women who are at higher risk of preterm birth. These include mothers with a history of preterm labor around the 24th week of gestation, those who experienced an early miscarriage, had multiple pregnancies or have a family history of preterm labor.

Mothers must watch out for symptoms like severe lower back pain or lower abdominal pain, unusual vaginal discharge, pelvic pressure and occurrence of contractions before time.

In case you notice any one of these, contact your doctor immediately. Your cervix will be checked for dilation and infection. If there is an infection, you will receive an immediate treatment.

If the doctors notice that your cervical length is decreasing and the cervix is dilating, a cervical cerlage is performed—it involves sewing the cervix temporarily and removing them at the time of the labor. You will be advised to be complete on bed rest and stay hydrated—it will bring down the risk of preterm birth.

According to Mayo Foundation for Medical Education and Research (MFMER), there is a research going on a treatment that can reduce the risk of preterm delivery. The treatment involves using a form of hormone progesterone placed as a silicon device around the cervix to prevent a preterm delivery in mothers with shorter cervical length.1

Moms must contact their gynecologists if they are concerned about their cervical length—they will always be the best person to guide you.