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Formal name: Fetal Fibronectin

The Test Sample

What is being tested?

Fetal fibronectin (fFN) is a glycoprotein that can be used to help predict the short term risk of premature delivery. fFN is produced at the boundary between the amnionic sac (which surrounds the baby) and the lining of the mother's uterus (the decidua) in an area called the uteroplacental (or choriodecidual) junction. Fetal fibronectin is largely confined to this junction and is thought to help maintain the integrity of the boundary. fFN is normally detectable in cervicovaginal fluid during early pregnancy and, in a normal pregnancy, it is no longer detectable after 24 weeks. However, it reappears and is again detectable after about 36 weeks.

According to the American College of Obstetricians and Gynecologists (ACOG), a normal pregnancy is 40 weeks, with a woman going into labor between 37 and 42 weeks. Finding fFN in cervicovaginal fluids after 36 weeks is not unusual as it is often released by the body as it gets ready for childbirth. The elevated fFN found in vaginal fluids early in pregnancy may simply reflect the normal growth and establishment of tissues at the uteroplacental junction, with levels falling when this phase is complete. What is known is that fFN should not be detectible between 22 and 35 weeks of pregnancy. Elevated levels during this period reflect a disturbance at the uteroplacental junction and have been associated with an increased risk of preterm labor and delivery.

How is the sample collected for testing?

A swab is used to take a sample of cervical or vaginal fluid from the posterior portion of the vagina or from the area just outside the opening of the cervix.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

Anything that physically disturbs the cervix or uterus has the potential to elevate fFN levels. Therefore, cervicovaginal fluid samples should be collected before any physical examinations. Lubricants, lotions, soaps, and douches should be avoided. Semen may contain enough fFN to create a positive test result, so sexual intercourse should also be avoided within 24 hours of sample collection.