Fetal fibronectin is a protein that helps keep the amniotic sac attached to the wall of the uterus during pregnancy. If there is a problem with the amniotic sac staying attached to the uterus, high amounts of fetal fibronectin can end up in the vaginal fluid. This can mean there is an increased chance of having a preterm birth.
Fetal fibronectin testing is sometimes done when someone has symptoms of preterm labor. If the test is negative, you probably aren't having preterm labor. But if the test is positive, it doesn't mean for sure that you're having preterm labor.
For this test, a sample of fluid is collected from the vagina or the opening to the uterus (cervix). First, a tool called a speculum is placed in the vagina. It opens the vagina a little bit. Next, a sterile swab is used to absorb fluid from the cervix or vagina. The speculum is removed. Then the swab is sent to the lab for testing.
A negative test result is quite accurate. It shows that labor hasn't started. A positive test result means labor may have started. But false-positive results are common. They can occur if you have recently had:
A pelvic exam. To reduce the risk of a false-positive result, it's important that this test be done before a manual pelvic exam.
Bleeding from the vagina.
The fetal fibronectin test is:
Not useful as a routine test for high-risk pregnancies.
Helpful only if you have symptoms of preterm labor.
Author: Healthwise Staff Clinical Review Board: All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.