The cervix is typically around 3 to 5 centimeters long and gradually shortens during pregnancy. However, some women have a cervix that is shorter than average, which may cause problems during pregnancy.
The cervix has an internal and an external opening (also called the internal os and external os). The internal os opens into the uterus, and the external os opens into the vagina. During pregnancy, the cervical ossa close to keep the fetus in the uterus and open when it’s time for delivery.
Over the course of a pregnancy, the cervix shortens and becomes softer to make delivery possible. Some women have a shorter cervix. As their cervix shortens over the course of their pregnancy, it may become too short too soon, which increases the risk of preterm labor and premature birth.
The main cause for a short cervix during pregnancy is an insufficient or incompetent cervix. During pregnancy, the baby grows and becomes heavier, pressing on the cervix. If the cervix is short, it may open before the baby is ready to be born due to pressure from the baby. This condition is known as an insufficient or incompetent cervix.
The majority of pregnancy losses in the first trimester are due to chromosomal abnormalities, but an incompetent cervix is the cause of many losses during the second trimester. Fortunately, insufficient cervix is not very common. Only 1 in 100 pregnancies might result in an incompetent cervix.
In addition to a short cervix, one or more of the following conditions might lead to an insufficient cervix:
- An earlier cervix surgery
- Cervical trauma
- Malformed cervix as a result of a birth defect
- Trauma to the cervix from a miscarriage or abortion
- LEEP — loop electrocautery excision procedure, used to treat cervical dysplasia (abnormal cells)
- Uterine anomalies or cervical lacerations with vaginal delivery
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Although often asymptomatic, some women experience some mild short cervix symptoms. The symptoms usually appear between 14 and 20 weeks of pregnancy and include:
When your cervix is short, the risk of premature labor uprises. This is because the cervix might not stay closed the way it's supposed to during your pregnancy. Women who experience a short cervix during pregnancy are more likely to have preterm labor than women who have a longer and thicker cervix.
The good news is that there’s a treatment for a short cervix. Doctors may recommend a few different methods that will help you avoid premature birth. Regular prenatal care makes it possible for your doctor to discover and treat any problems with a short cervix in a timely manner.
A short cervix can’t be diagnosed by a manual exam. For the moment, ultrasound is the most reliable way to diagnose a short cervix.
During an ultrasound, your doctor will measure your cervical length. In a typical pregnancy, the cervix is usually between 3 and 5 centimeters long (or 30 to 50 mm). The risk of premature birth is greatest when your cervix is less than 2.5 centimeters long. Early detection of a short cervix during pregnancy can help prevent preterm birth and help women receive treatment on time.
The risk of premature birth due to a short cervix can be a source of worry for an expecting mother.
The good news is that there are ways to manage the risk of a short cervix and prolong the pregnancy. Treatment for a short cervix includes:
- Progesterone: Progesterone is a hormone that is used to prevent contractions and support a pregnancy until it reaches full term. Women can receive the hormone as a weekly injection or as a daily vaginal medication until around 34 to 36 weeks. A doctor may prescribe it in the second trimester or earlier.
- Arabin Pessary: Arabin Pessary is another way of reducing the chances of premature pregnancy. It’s a silicone ring that is inserted into the vagina to hold the cervix closed. This is not a surgical procedure, and the placement of the ring is done by an obstetrician. Arabin pessary placement can increase the risk of an infection.
- Cervical stitch/cerclage: during a cervical cerclage, a stitch is placed in the cervix to help it to stay closed. Cerclage is associated with an 85 to 90 percent successful pregnancy rate. The cerclage is maintained until 36 to 38 weeks of pregnancy if possible. This procedure is offered to women who have had one or more premature deliveries or late miscarriages or have had cervical surgery in the past.
If the diagnosis of the short cervix is made, betamethasone may be taken between 24 and 34 weeks of gestation to decrease the risk of premature birth. Strict bed rest may be recommended as a precautionary measure.
Doctors generally will also suggest regular monitoring and a consultation with a physician who specializes in high-risk pregnancies. In this way, any issues with a short cervix during pregnancy can be found and treated early.