The cervix, a muscular, tunnel-like organ, is located at the lower end of the uterus and connects to the vagina. During pregnancy, its primary function is to maintain the fetus within the uterus by remaining closed and firm. It also secretes a thick mucus plug that seals the entry to the uterus, protecting the developing baby from infections. Cervical length refers to the measurement of this canal, from its internal to external opening. This measurement is a common aspect of prenatal care, providing information about the cervix’s ability to support the pregnancy.
Why Cervix Length Measurement is Important
Measuring cervical length is a significant step in assessing the risk of preterm birth, which occurs when a baby is born before 37 weeks of pregnancy. This is because the cervix naturally shortens and softens as the body prepares for labor, but if this process happens too early, it can lead to complications. Healthcare providers often recommend cervical length measurements for individuals with specific risk factors. Those with a history of spontaneous preterm birth, a previous second-trimester pregnancy loss, or past cervical surgery (such as a cone biopsy or LEEP procedure) are typically monitored more closely. Additionally, women carrying multiple pregnancies may also be considered for this assessment due to their elevated risk.
The Measurement Procedure
Cervical length measurement is primarily performed using a transvaginal ultrasound, which is considered the most accurate method. During this procedure, the patient typically lies on an exam table with knees bent, similar to a gynecological exam. A small, lubricated ultrasound probe, or transducer, is gently inserted a few inches into the vagina. This probe emits sound waves that create detailed images of the cervix on a screen, allowing the healthcare provider to measure its length precisely. The procedure is generally not painful, though some individuals might feel minor pressure from the probe.
For optimal results, the bladder should be empty or nearly empty before the scan. The measurement is commonly performed during the mid-trimester, typically between 18 and 24 weeks of gestation, often coinciding with the routine anatomy scan. However, for individuals with a history of preterm birth or other concerns, measurements might begin as early as 16 weeks.
Understanding Your Cervical Length Results
When interpreting cervical length results, healthcare providers consider the measurement, typically given in millimeters, in conjunction with the gestational age. A cervix is generally considered short if it measures less than 25 millimeters (2.5 centimeters) before 24 weeks of pregnancy. For instance, a normal cervical length at 20 weeks is often around 30-40 mm. A measurement below 25 mm is associated with an increased risk of preterm birth. Some medical guidelines may even consider lengths between 20-30 mm as short.
It is important to note that while a shorter cervix indicates a higher risk, many individuals with a short cervix still carry their pregnancies to term. They will consider individual patient history, other risk factors, and the overall clinical picture. These measurements are dynamic and can vary slightly throughout pregnancy, making consistent professional evaluation important.
Managing a Short Cervix
If a short cervix is detected, several medical interventions and monitoring strategies are available to help prolong the pregnancy. One common approach is progesterone supplementation, often administered vaginally. Progesterone is a hormone that can help reduce the risk of preterm birth in individuals with a short cervix, typically started before 24 weeks and continued until around 36 weeks of pregnancy.
Another intervention is cervical cerclage, a surgical procedure where a stitch is placed in the cervix to help keep it closed. This procedure is usually considered for individuals with a history of preterm birth or those whose cervix is very short, sometimes less than 10 mm. The cerclage is typically removed around 36-37 weeks of pregnancy. Increased monitoring through serial ultrasound scans may also be recommended to track changes in cervical length. The specific management plan is highly individualized, taking into account the degree of cervical shortness, the patient’s medical history, and other risk factors.