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. If this connection is disrupted, fetal fibronectin can be released into secretions near your cervix. The connection can be disrupted by an infection, inflammation, the separation of the placenta from the wall of the uterus, uterine contractions or shortening of the cervix.

If your health care provider is concerned about preterm labor, he or she might test a swab of these secretions 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 premature birth within seven days.

However, keep in mind that research hasn't shown this test to improve outcomes immediately before and after childbirth.

Why it's done

The fetal fibronectin test is used to rule out preterm labor. It can provide valuable information if you have signs or symptoms of preterm labor.

If the fetal fibronectin test is positive, your health care provider may take steps to address premature birth — such as administering medication to enhance the baby's lung maturity.

Risks

The fetal fibronectin test is a simple procedure. However, false-positive results can occur.

How you prepare

To avoid a false-positive result, the test will be done before any pelvic exam or transvaginal ultrasound. These tests can cause a release of fetal fibronectin and lead to a false-positive result. Intercourse and vaginal bleeding can affect the test results, too. If you experience vaginal bleeding or have had sex within the last 24 hours, the test probably won't be done.

Also, avoid using douches or lubricants or placing medications in your vagina shortly before the test. They also can affect test results.

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 your cervix.

After the procedure

The sample will be sent to a lab for analysis.

In some cases, a transvaginal 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 secretions. If you have a positive result between weeks 22 and 34, you're at increased risk of premature birth within seven days.

    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 temporarily stop 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.

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 sensations of abdominal tightening (contractions)
  • Constant low, dull backache
  • A sensation of pelvic or lower abdominal pressure
  • Mild abdominal cramps
  • Vaginal spotting or bleeding
  • Preterm rupture of the membranes — in a gush or a continuous trickle of fluid after the membrane around the baby breaks or tears
  • A change in type of vaginal discharge — watery, mucuslike or bloody
May 10, 2019
References
  1. Lockwood CJ. Preterm labor: Clinical findings, diagnosis evaluation, and initial treatment. https://www.uptodate.com/contents/search. Accessed March 7, 2019.
  2. American College of Obstetricians and Gynecologists (ACOG) Committee on Practice Bulletins — Obstetrics. ACOG Practice Bulletin No. 130: Prediction and prevention of preterm birth. Obstetrics and Gynecology. 2012;120:964. Reaffirmed 2018.
  3. Gabbe SG, et al., eds. Preterm labor and birth. In: Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, Pa.: Elsevier; 2017. https://www.clinicalkey.com. Accessed March 7, 2019.
  4. Berghella V, et al. Fetal fibronectin testing for prevention of preterm birth in singleton pregnancies with threatened preterm labor: a systematic review and metaanalysis of randomized controlled trials. American Journal of Obstetrics and Gynecology. 2016;215:431.
  5. McLaren JS, et al. Prediction of spontaneous preterm birth using quantitative fetal fibronectin after recent sexual intercourse. American Journal of Obstetrics and Gynecology. 2015;212:89.

Fetal fibronectin test