During pregnancy, a uterine infection causes
inflammation, which can trigger preterm labor. This
inflammation can also stimulate the
amnion cells to produce fetal fibronectin, a protein.
Fetal fibronectin testing is sometimes done when preterm labor
symptoms are present. When the fetal fibronectin test is negative, it is
unlikely that you are having preterm labor. But even if the test is positive,
it does not mean for sure that you are having preterm labor.
For fetal fibronectin testing, a sample of fluid
is collected from the vagina or the opening to the uterus (cervix). First, a
speculum is used to spread the walls of the vagina to view the cervix. Next, a
sterile swab is used to absorb fluid from the cervix or vagina. The speculum is
removed and the swab is sent to the laboratory for testing.
A negative test result is quite accurate and shows that labor
has not started. A positive test result may show that
labor has started, but false-positive results are common. False-positive
results can occur if a woman has recently had:
A pelvic exam. To reduce the risk of a
false-positive result, it is important that a fetal fibronectin test be done
before a manual pelvic exam.
Bleeding from the
The fetal fibronectin test is:
Somewhat expensive and may not be available in all medical
Not useful for predicting labor in women at risk
for preterm labor.
Helpful only for women with symptoms of preterm