During pregnancy, what's the significance of cervical length?
Answer From Yvonne Butler Tobah, M.D.
Cervical length refers to the length of the lower end of your uterus. During pregnancy, the length of the cervix might shorten too soon, increasing the risk of preterm labor and premature birth. Preterm labor is labor that begins before week 37 of pregnancy. The earlier premature birth happens, the greater the health risks for your baby.
Before pregnancy, your cervix — the lower part of the uterus that connects to the vagina — is normally closed, rigid and at least 3 centimeters long. During pregnancy, your cervix will gradually soften. As your body gets ready for labor, the cervix decreases in length, becomes thinner and finally opens as you prepare to give birth. If your cervix begins to open before 37 weeks, you could give birth prematurely.
If you experience signs and symptoms of preterm labor — such as regular or frequent contractions, a constant low, dull backache, vaginal spotting, or pelvic pressure — your health care provider might do a pelvic exam to determine if your cervix has begun to open. He or she might also do an ultrasound to measure your cervical length.
If you're in preterm labor, your health care provider will explain possible treatments and the risks and benefits of trying to stop or delay your labor. If you're not in active preterm labor but meet certain criteria, such as painless cervical dilation in the second trimester before week 24 of pregnancy, your health care provider might recommend a cervical cerclage. During this surgical procedure, the cervix is stitched closed with sutures.
If you have a prior history of premature birth, your health care provider might also discuss giving you progesterone injections to decrease your risk of another premature birth.
If you're concerned about your cervical length during pregnancy, consult your health care provider. He or she can answer your questions and help you understand how to promote a healthy pregnancy.
Yvonne Butler Tobah, M.D.
May 10, 2018
- Frequently asked questions. Labor, delivery, and postpartum care FAQ087. Preterm (premature) labor and birth. American College of Obstetricians and Gynecologists. https://www.acog.org/Patients/FAQs/Preterm-Premature-Labor-and-Birth. Accessed April 11, 2018.
- Butler Tobah YS (expert opinion). Mayo Clinic, Rochester, Minn. April 19, 2018.
- Berghella V, et al. Cervical insufficiency. https://www.uptodate.com/contents/search. Accessed April 11, 2018.
- Norwitz ER. Transvaginal cervical cerclage. https://www.uptodate.com/contents/search. Accessed April 11, 2018.
- American College of Obstetricians and Gynecologists (ACOG) Committee on Practice Bulletins — Obstetrics. ACOG Practice Bulletin No. 142: Cerclage for the Management of Cervical Insufficiency. Obstetrics & Gynecology. 2014;123:372.
- Conde-Agudelo A, et al. Vaginal progesterone to prevent preterm birth in pregnant women with a sonographic short cervix: Clinical and public health implications. American Journal of Obstetrics and Gynecology. 2016;214:235.