The cervix, a part of the female reproductive system, can be visualized using ultrasound technology. This common and safe imaging technique is frequently employed during pregnancy to assess structures within the uterus, including the cervix.
Methods of Cervical Visualization
Ultrasound offers different approaches to visualize the cervix, primarily transabdominal and transvaginal methods. Each technique provides advantages for cervical imaging, depending on the clinical need.
Transabdominal ultrasound (TAUS) involves placing the transducer on the abdomen to generate images. This non-invasive method is often used for general fetal assessments. However, for detailed cervical imaging, especially length measurement, TAUS may be less accurate due to factors like bladder fullness or the position of other organs.
For a more precise and detailed view of the cervix, transvaginal ultrasound (TVUS) is preferred. This method involves inserting a smaller, specialized transducer into the vagina, positioning it closer to the cervix. TVUS provides clearer images and more accurate measurements of cervical length, making it the preferred method for assessing the cervix during pregnancy. While transabdominal ultrasound can identify women at low risk for a short cervix, a transvaginal scan is often needed for definitive assessment.
Importance of Cervical Assessment
Assessing the cervix during pregnancy is important for its role in maintaining the pregnancy and preventing preterm birth. The cervix normally remains long and closed throughout most of pregnancy, acting as a barrier to the uterus. If it shortens or opens too early, it can increase the risk of premature delivery.
Measuring cervical length through ultrasound serves as a screening tool to identify individuals at higher risk of preterm birth. A shortened cervix can indicate conditions like cervical insufficiency, where the cervix painlessly dilates prematurely. Early detection allows healthcare providers to consider interventions aimed at prolonging pregnancy and improving outcomes for the baby.
Understanding Cervical Measurements
When sonographers assess the cervix via ultrasound, they focus on its length and any signs of opening or changes in its structure. Cervical length refers to the measurement from the internal opening (internal os) to the external opening (external os). In a healthy pregnancy, the cervix is long and closed.
While specific measurements can vary, a normal cervical length is generally around 4 cm until late in gestation. A cervical length measuring less than 2.5 cm before 24 weeks is considered a shortened cervix, indicating an increased risk of preterm birth. Sonographers also look for “funneling,” which is when the internal cervical canal begins to open and take on a funnel shape. The presence of funneling can suggest a higher risk of preterm delivery.