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Introduction ⬇

The fetal fibronectin (fFN) test helps to predict a preterm delivery when the presenting symptoms are questionable so that early intervention (e.g., tocolytics, corticosteroids, transport to a tertiary center) can be initiated when indicated. fFN is secreted in early pregnancy to help attach the fertilized egg to the implantation site in the uterus, but it is not secreted after 22 weeks until near term. This test detects preterm labor from 24 until 34 weeks’ gestation.

This test is performed for women with intact membranes and cervical dilation less than 3 cm.

fFN is abundant in amniotic fluid and may be useful in the diagnosis of ruptured membranes. The detection of fFN in vaginal secretions before membrane rupture may be a marker for impending preterm labor within the next 7–14 days.

Procedure ⬆ ⬇

  1. Using a sterile speculum, obtain secretions from the cervix and vagina by rotating a sterile Dacron swab near the outside of the cervix and the posterior fornix of the vagina. Observe standard precautions.

  2. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered. Place specimen in a biohazard bag and send the specimen to laboratory. Results may take 24–48 hours.

Procedural Alert

Specimens for fFN should be obtained before digital cervical examination, collection of culture specimens, vaginal ultrasound examination, or any prior manipulation of the cervix because this can result in release of fFN and false results

Clinical Implications ⬆ ⬇

A level of fFN equal to or greater than a reference value (0.050 μg/mL) is considered positive and means that preterm labor is imminent. Transvaginal cervical ultrasonography may be used along with fFN to assess risk for preterm birth. A short cervix (<25 mm) with a positive fFN is a strong predictor of preterm delivery. The greatest value of this testing is a negative result in order to avoid unnecessary interventions.

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and procedure to the patient.

  2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Counsel the patient regarding test results and need for follow-up treatment or preparation for probable delivery.

  2. Be sure the patient knows the warning signs of preterm labor.

    1. Uterine contractions—a hard feeling over the entire surface of the uterus that lasts 20 seconds or longer. The contractions can be painless. If more than four are felt per hour, notify healthcare provider

    2. Menstrual-like cramps felt low in abdomen; may be constant or come and go

    3. Pelvic pressure or fullness in the pelvic area or back of the thighs

    4. Backache—a dull pain in the lower back, either constant or rhythmic, that is not relieved by changing positions

    5. Persistent diarrhea

    6. Intestinal cramps with or without diarrhea

    7. Vaginal discharge that is greater than normal or changes in consistency or color (especially if it is pink, bloody, or greenish)

    8. A general feeling or sense that something is wrong

  3. Explain the possible causes and increased risks associated with preterm labor and birth:

    1. Past preterm birth

    2. Spontaneous miscarriage in second trimester

    3. Uterine anomaly

    4. Diethylstilbestrol exposure

    5. Incompetent cervix

    6. Hydramnios

    7. Bleeding in second and third trimester

    8. Preterm labor

    9. Premature rupture of membrane

    10. Multiple gestation

    11. Preterm cervical dilation >2 cm (multipara) or >1 cm (primipara)

    12. Pregnancy weight <115 pounds

    13. Patient <15 years of age

  4. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆ ⬇

  1. Vaginal bleeding

  2. Ruptured membranes

  3. Sexual intercourse within 24 hours of collection

Reference Values ⬆

Normal