Many research studies are focusing on the important question of which pregnant women are at greater risk of preterm labor. By identifying which women are at increased risk, health care providers can provide early interventions, treatments, and close monitoring of these pregnancies to try and reduce the chances that the infant will be born preterm.
What does it mean if I have a shortened cervix?
As a preparation for birth, the cervix (the lower part of the uterus) naturally shortens late in pregnancy. However, having a prematurely shortened cervix, around the fourth or fifth month of pregnancy, increases the risk of delivering preterm.
An ultrasound can be done to evaluate a woman's cervix during pregnancy. Transvaginal ultrasound scans to measure cervical length can identify women with a shortened cervix.
What does it mean if I have an "incompetent" cervix?
Doctors may refer to a cervix that begins to open before an infant is ready to be born as an "incompetent" cervix. The process of cervical opening is painless and unnoticeable, without labor contractions or cramping. The cervix (the neck of the uterus) normally stays tightly closed during pregnancy. A cervix that starts to open early can lead to miscarriage. For some women, this happens again in later pregnancies. This may be due to cervical weakness (incompetence) if the miscarriage occurred in the second or early third trimester.1
Approximately 5 to 10 out of 1,000 pregnant women are diagnosed as having an incompetent cervix.2 Often what is meant is that the cervix is shortened, but some women may have abnormalities of the cervix that make it harder for the cervix to remain closed during pregnancy.
To try to prevent preterm labor and birth, a doctor may place a stitch around the cervix to keep it closed. This procedure is called cervical cerclage (pronounced sair-KLAZH). NICHD research has found that, in women with a prior preterm birth who have a short cervix, cerclage may improve their prospects for normal birth.3
What is the fetal fibronectin (fFN) test?
The fetal fibronectin (fFN; pronounced fy-broh-NEK-tun) test is used to detect whether the protein fFN is being produced. Fetal fibronectin is like a biological "glue" between the uterine lining and the pregnancy.
Normally fFN can be detected in the pregnant woman's secretions from the vagina and cervix early in the pregnancy (up to 22 weeks, or about 5 months) of pregnancy and again toward the end of the pregnancy (1 to 3 weeks before labor). It is usually not present between 24 and 34 weeks of pregnancy (5½ to 8½ months). If fFN is detected during this time, it may be a sign that the woman may be at risk of preterm labor and birth.
Testing for fFN can predict with about 50% accuracy which pregnant women showing signs of preterm labor are likely to have a preterm birth.4 It is typically used for its negative predictive value, meaning that if it is negative, it is unlikely that a woman will deliver within the next 7 days.
- Drakeley, A. J., Roberts, D., & Alfirevic, Z. (2003; published online 2010). Cervical stitch (cerclage) for preventing pregnancy loss in women. Cochrane Database of Systematic Reviews, 1, Retrieved May 4, 2012, from, http://summaries.cochrane.org/CD003253/cervical-stitch-cerclage-for-preventing-pregnancy-loss-in-women [top]
- Denney, J. M., Culhane, J. F., & Goldenberg, R. L. (2008, November 5). Prevention of preterm birth. Women's Health, 4, 625–638. Retrieved April 17, 2012, from http://www.medscape.com/viewarticle/582761_10 [top]
- Owen, J., Hankins, G., Iams, J. D., Berghella, V., Sheffield, J. S., Perez-Delboy, A., et al. (2009, October). Multicenter randomized trial of cerclage for preterm birth prevention in high-risk women with shortened midtrimester cervical length. American Journal of Obstetrics & Gynecology, 201(4), 375.e1–375.e8. Retrieved July 5, 2012, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2768604 [top]
- Goldenberg, R., Mercer, B., Meis, P., Copper, R., Das, A., McNellis, D., & the NICHD Maternal Fetal Medicine Units Network. (1996). The Preterm Prediction Study: Fetal fibronectin testing and spontaneous preterm birth. Obstetrics & Gynecology, 87, 643–648. [top]