Overview

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.

Risks

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.

Other precautions

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

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
Jan. 03, 2018
References
  1. Lockwood CJ. Diagnosis of preterm labor and overview of preterm birth. http://www.uptodate.com/home. Accessed Feb. 21, 2016.
  2. Fetal fibronectin. Lab Tests Online. https://labtestsonline.org/understanding/analytes/ffn/tab/sample/. Accessed Feb. 20, 2016.
  3. DeFranco EA, et al. Improving the screening accuracy for preterm labor: Is the combination of fetal fibronectin and cervical length in symptomatic patients a useful predictor of preterm birth? A systematic review. American Journal of Obstetetrics and Gynecology. 2013;208:233.
  4. Van Baaren GJ, et al. Risk factors for preterm delivery: Do they add to fetal fibronectin testing and cervical length measurement in the prediction of preterm delivery in symptomatic women? European Journal of Obstetrics & Gynecology and Reproductive Biology. 2015;192:79.
  5. McLaren JS, et al. Prediction of spontaneous preterm birth using quantitative fetal fibronectin after recent sexual intercourse. American Journal of Obstetetrics and Gynecology. 2015;212:89.
  6. Wick MJ (expert opinion). Mayo Clinic, Rochester, Minn. March 23, 2016.

Fetal fibronectin test