Fetal fibronectin test
Medically reviewed on Jan 3, 2018
Fetal fibronectin is a protein that's believed to help keep the amniotic sac "glued" to the lining of the uterus. The amniotic sac is the fluid-filled membrane that cushions your baby in the uterus.
Fetal fibronectin is often present in vaginal discharge before week 22 of pregnancy. Fetal fibronectin also begins to break down and can be detected in vaginal discharge toward the end of pregnancy.
If your health care provider is concerned about preterm labor, he or she might test a swab of secretions near your cervix for the presence of fetal fibronectin between week 22 and week 34 of pregnancy. A positive fetal fibronectin test is a clue that the "glue" has been disturbed and you're at increased risk of preterm labor.
Why it's done
The fetal fibronectin test is used to rule out preterm labor. It's generally not useful for women who are at low risk of preterm labor, but it can provide valuable information for women who have signs or symptoms of preterm labor or those who are at high risk of preterm labor.
If the fetal fibronectin test is positive, your health care provider will take steps to address premature birth — such as administering medication to enhance the baby's lung maturity. If the fetal fibronectin test is negative, you can be assured that you're unlikely to deliver within the next two weeks.
The fetal fibronectin test is a simple procedure. However, false-positive results are common, which might cause unnecessary anxiety or treatments.
How you prepare
You don't need to do anything special to prepare for the fetal fibronectin test.
To avoid a false-positive result, the test will be done before any pelvic exam or vaginal ultrasound. Avoid having sex for 24 hours before the test. Also, avoid using douches, lotions and soaps, which can affect test results, for at least a day before the test.
Vaginal bleeding can affect the test results, too. If you experience vaginal bleeding, the test probably won't be done.
If the amniotic sac ruptures — your water breaks — the test won't be done. The amniotic sac is a fluid-filled membrane that cushions your baby in the uterus.
What you can expect
During the procedure
During the fetal fibronectin test, you'll lie on your back on an exam table. Your health care provider will place a speculum in your vagina and use a cotton swab to gently swipe secretions near the cervix.
After the procedure
This sample will be sent to a lab for analysis. Results are typically available within a few hours.
In some cases, a vaginal ultrasound is done after the sample is taken to measure the length of your cervix. During the ultrasound, you'll lie on your back and your health care provider or technician will place a slender, wandlike device in your vagina. The device uses sound waves to digitally create images on a monitor.
Results of the fetal fibronectin test are either positive or negative:
Positive. A positive result means that fetal fibronectin is present in your cervical fluid. If you have a positive result between weeks 22 and 34, you're at increased risk of preterm labor.
Your health care provider might take steps to prepare for a potentially early birth, such as giving you steroids to speed your baby's lung maturity. Or, you might be given medications to decrease the risk of neurological complications, such as cerebral palsy, in your infant. If you're having contractions, you might be given drugs to decrease them.
- Negative. A negative result means that fetal fibronectin isn't present in your cervical fluid. This indicates that you aren't likely to deliver in the next two weeks. In fact, a negative result might be the most powerful benefit of the test — allowing you and your health care provider to relax a bit with the knowledge that a premature birth isn't imminent.
Whether your test results are positive or negative, remember that prompt recognition of preterm labor might give your health care provider a chance to delay premature birth or improve your baby's readiness for birth.
If you're concerned that you might be going into labor early, contact your health care provider. Don't worry about mistaking false labor for the real thing.
Warning signs of preterm labor include:
- Regular or frequent contractions — a tightening sensation in the abdomen
- Constant low, dull backache
- A sensation of pelvic or lower abdominal pressure
- Mild abdominal cramps
- Vaginal spotting or bleeding
- Watery vaginal discharge (water breaking) — in a gush or a trickle
- A change in vaginal discharge