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The cervix is the cylindrical part of the uterus that connects the uterus to the vagina. Before pregnancy, the cervix is closed, long, and firm. Its main role is to secrete fluids that help sperm travel from the vaginal canal to the uterus.
The cervix is typically around 3–5 centimeters long and gradually shortens during pregnancy. However, sometimes the cervix is shorter than average, which may cause issues during pregnancy. What does a “short cervix” mean?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 then open when it’s time for delivery. Over the course of a pregnancy, the cervix shortens and becomes softer to make delivery possible. Some people naturally have a shorter cervix. As their cervix shortens throughout their pregnancy, it may become too short too soon, which increases the risk of preterm labor and premature birth. A short cervix is less than 25 millimeters in length at 18–24 weeks’ gestation. Health care providers measure the length of the cervix with an ultrasound scan.
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, the pressure from the baby may cause it to open before the baby is ready to be born. This condition is known as an insufficient or incompetent cervix. Most 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. Insufficient cervix is not very common, however. Only one 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:
Although often asymptomatic, some mild short cervix symptoms are possible. The symptoms usually appear between 14 and 20 weeks of pregnancy and include:
When the cervix is short, the risk of premature labor and pregnancy loss rises. This is because the cervix might not stay closed for as long as it’s supposed to during pregnancy. Those with a short cervix during pregnancy are more likely to have preterm labor than those with a longer and thicker cervix. There is treatment for a short cervix. Health care providers may recommend a few different methods to help avoid premature birth. Regular prenatal care makes it possible for a health care provider to discover and treat issues associated with a short cervix in a timely manner. Short cervix diagnosisA short cervix can only be detected during pregnancy. A short cervix can’t be diagnosed by a manual exam, but a physical exam can help the health care provider see if the amniotic sac has begun to protrude through the opening (prolapsed fetal membranes). A transvaginal ultrasound is the most reliable way to diagnose a short cervix. During an ultrasound, a health care provider will measure the cervical length. In a typical pregnancy, the cervix is usually between 3–5 centimeters long (30 to 50 millimeters). The risk of premature birth is greatest when the cervix is less than 2.5 centimeters long. Early detection of a short cervix during pregnancy can help prevent preterm birth and begin treatment before it causes any complications.
The risk of premature birth and pregnancy loss due to a short cervix can be concerning. There are ways to manage the risk of a short cervix and prolong the pregnancy. Treatment for a short cervix includes:
If the diagnosis of a short cervix is made, betamethasone may be used between 24 and 34 weeks of gestation to improve newborn outcomes. Strict bed rest may be recommended as a precautionary measure. Health care providers will generally 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. Yvonne Butler Tobah, “Cervical Length: Why Does It Matter during Pregnancy?” Mayo Clinic, Mayo Foundation for Medical Education and Research, 28 Apr. 2020, www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/expert-answers/cervical-length/faq-20058357. Withanawasam, Neoma, and Sanyogita Tara. “The shortened cervix in pregnancy: Investigation and current management recommendations for primary caregivers.” Australian journal of general practice vol. 48,3 (2019): 121-123. doi:10.31128/AJGP-09-18-4708 “Incompetent Cervix.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 25 July 2019, www.mayoclinic.org/diseases-conditions/incompetent-cervix/diagnosis-treatment/drc-20373842. “Antenatal Corticosteroid Therapy for Fetal Maturation.” ACOG, August 2017, www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/08/antenatal-corticosteroid-therapy-for-fetal-maturation. “Incompetent Cervix.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 25 July 2019, www.mayoclinic.org/diseases-conditions/incompetent-cervix/symptoms-causes/syc-20373836. How much thought do you really give to your cervix, the cylinder-shaped piece of tissue that connects the vagina with the uterus? When you're pregnant, your cervix takes center stage, opening up and thinning out to allow your baby to pass through the birth canal. So if you find out you have a short cervix, you may wonder how it will affect your labor and delivery and, of course, your baby. Try not to worry and know that while a short cervix could potentially cause some complications, there are effective treatments available to address this condition so women can go on to have healthy pregnancies. Here’s what you need to know about having a short cervix when you're pregnant. What does it mean to have a short cervix?Having a short cervix means exactly what it sounds like: Your cervix happens to be shorter in length than it is for other women. Before and during pregnancy, the cervix is typically between 30 and 50 millimeters long, but occasionally a mom-to-be will have a cervix that’s a bit shorter, even under 25 millimeters long (and no, your cervix can’t be coaxed to grow). A short cervix can mean you’re more likely to have cervical insufficiency (also called an incompetent cervix), which is when your cervix dilates or opens up too soon. This condition is called premature cervical effacement (thinning) and dilation and it can raise your risk of premature labor, early delivery and even pregnancy loss. Does a short cervix affect my ability to get pregnant?While your ability to become pregnant shouldn’t be impacted by a short cervix, having any kind of structural abnormality of this body part can affect your ability to carry a baby the full nine months of pregnancy. Your doctor might perform an ultrasound to check your cervical length or a pelvic exam, especially if you show signs of preterm labor (contractions, backache). What causes a short cervix?It’s not clear why some women have a shorter cervix than others or why the condition can lead to cervical insufficiency, which may be congenital in some women. Still, there are several factors that may come into play, including the following:
Short cervix diagnosisIf you’re experiencing any signs of preterm labor, such as contractions, vaginal discharge, pelvic pressure or backache, your practitioner might order a transvaginal ultrasound to measure your cervical length. This type of ultrasound is internal and uses a transducer to get a good look at your cervix. A pelvic exam could also be performed to see if your cervix has started to open. Short cervix treatmentShort cervix treatment options usually depend on the measurements your doctor has taken, how far along you are in your pregnancy and whether you’re carrying one baby or multiples. Here’s more about treating a short cervix with ultrasound, hormone therapy and surgery.
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