What Is Cervical Funneling?
Cervical funneling refers to the dilation of the internal os, the opening closest to the uterus, and shortening of the cervical canal. Normally, the cervix remains long and closed, acting as a strong barrier. When funneling occurs, the cervix takes on a “V” or “U” shape on ultrasound as the internal opening widens.
Cervical length, measured from the internal to external os, indicates this change. A normal length is typically 30-50 mm (3-5 cm) during the second trimester. Funneling is identified when the internal os dilates and the functional length shortens, sometimes to less than 25 mm before 24 weeks. The degree of funneling and shortening helps providers evaluate its significance.
Causes of Cervical Funneling
Several factors can contribute to cervical funneling. A common reason is cervical insufficiency, also known as an incompetent cervix, where the cervix opens without contractions. This condition can be present from birth or develop due to previous trauma or procedures. Prior cervical surgeries, such as a loop electrosurgical excision procedure (LEEP) or cone biopsy, can weaken its structure and increase funneling risk.
Carrying multiple pregnancies, like twins or triplets, places increased pressure on the cervix, leading to premature shortening and funneling. Uterine abnormalities, including congenital structural issues, may also predispose a person to cervical changes. A history of preterm birth in a previous pregnancy is a significant indicator, suggesting a predisposition to cervical changes. In some cases, the specific cause remains unknown.
Implications for Your Pregnancy
Cervical funneling increases the risk of preterm birth. When the internal opening of the cervix widens and shortens, it reduces the cervix’s structural integrity to hold the pregnancy to term. This diminished support means the cervix is less able to withstand the growing pressure of the uterus and fetus. Premature changes in cervical length and shape can signal the body is preparing for labor earlier than expected.
A shortened and funneled cervix provides less barrier against ascending infections, which can contribute to preterm labor risk. The extent of cervical shortening and funneling directly correlates with the increased probability of delivering before 37 weeks. While cervical funneling does not guarantee preterm birth, it is a significant finding that prompts closer monitoring and potential interventions to prolong pregnancy.
Management and Monitoring
When cervical funneling is detected, healthcare providers typically initiate close monitoring and potential interventions. Regular transvaginal ultrasounds are often performed to track changes in cervical length and the degree of funneling over time. This ongoing assessment helps determine the progression of cervical changes and guide management decisions.
One common intervention is progesterone supplementation, often administered vaginally, which can help maintain uterine quiescence and strengthen the cervix. For certain individuals, particularly those with a history of preterm birth or significant cervical shortening, a cervical cerclage may be recommended. This procedure involves placing a stitch around the cervix to provide mechanical support and help keep it closed. While strict bed rest is generally not advised, activity modification might be discussed, which could involve reducing strenuous activities to minimize pressure on the cervix. These management strategies aim to prolong the pregnancy and improve outcomes for the baby.