Foetal Fibronectin Test: Predicting Preterm Labor

What Is a Foetal Fibronectin Test?

The foetal fibronectin test is a diagnostic procedure used during pregnancy to evaluate the risk of preterm labour. Foetal fibronectin (fFN) is a glycoprotein that acts like a "glue", helping the amniotic sac adhere to the uterine lining, particularly in early pregnancy and again close to term. Normally, fFN is not present in significant quantities in vaginal secretions between 22 and 34 completed weeks of gestation. However, if fFN is present during this period, it may indicate that the bond between the amniotic sac and uterus is weakening, increasing the risk of preterm labour.

When Is the fFN Test Recommended?

Your doctor may recommend an fFN test if:

• You're between 24 and 34 weeks pregnant
• You're experiencing symptoms of preterm labor, such as regular uterine contractions, pelvic pressure, or low back pain
• You have risk factors for premature delivery, like a prior preterm birth, short cervix, or certain infections
• You require an assessment to rule out preterm labor or guide management decisions

The test is most useful for predicting imminent preterm delivery within the next 7–14 days in symptomatic women between 24 and 34 weeks’ gestation.

Why Is the fFN Test Recommended?

The foetal fibronectin test serves several important purposes:

• Assessing the short-term risk of preterm birth in women with signs and symptoms of preterm labor
• Helping to differentiate between true and false labor
• Guiding decisions about hospitalization, closer monitoring, or medications to delay delivery
• Supporting informed discussions about prognosis and potential interventions
• Avoiding unnecessary treatments in those with negative results and low risk

By identifying women at high risk of delivering prematurely, the fFN test allows for timely interventions to improve neonatal outcomes.

How Is the fFN Test Performed?

The fFN test procedure is relatively simple and can be done in a doctor's office or hospital:

1. A speculum is inserted into the vagina, similar to during a Pap smear.
2. A swab is used to collect a sample of fluid from the posterior fornix, an area near the cervix.
3. The swab is then sent to a lab for analysis or tested on-site with a rapid kit.

The whole process takes only a few minutes. You may feel some discomfort or pressure during the speculum exam, but it shouldn't be painful.

What Are the Uses of the Foetal Fibronectin Test?

The foetal fibronectin test has several important uses in pregnancy management:

• Assessing preterm labor risk in symptomatic women between 24-34 weeks gestation
• Guiding decisions about initiating treatments like corticosteroids for fetal lung maturity or tocolytic medications to halt contractions
• Determining whether hospital admission or transfer to a facility with NICU capabilities is necessary
• Providing reassurance and avoiding unnecessary interventions when the risk of preterm birth is low, as indicated by a negative fFN test result.

What Do fFN Test Results Mean?

fFN test results are reported as either positive or negative, indicating the presence or absence of foetal fibronectin above a certain threshold.

Here's what they mean:

• A positive result (fFN ≥50 ng/mL) suggests an increased risk of spontaneous preterm delivery, often within 7-14 days. It indicates the "glue" bonding the amniotic sac to the uterus may be weakening.
• A negative result (fFN <50 ng/mL) indicates a low likelihood of preterm birth in the near term. It provides reassurance and helps avoid unnecessary treatments or hospitalisations.

The foetal fibronectin test accuracy for predicting preterm birth is high but works best when combined with other clinical findings and risk factors.

How to Prepare for a Foetal Fibronectin Test?

Preparing for an fFN test is quite straightforward:

• Avoid sexual intercourse, digital or speculum examinations, or use of vaginal creams/medications for at least 24 hours before the test
• Inform your doctor if you've had any recent vaginal bleeding or procedures
• Empty your bladder prior to the test, although this isn't always required

No special preparations like fasting are necessary.

What Factors Can Affect fFN Test Results?

Certain factors can influence foetal fibronectin test accuracy, potentially causing false-positive or false-negative results:

• Recent sexual intercourse or vaginal examinations
• Presence of vaginal infections, such as bacterial vaginosis or trichomoniasis
• Active vaginal bleeding
• Use of vaginal lubricants or medications prior to sample collection
• Cervical inflammation or recent procedures involving the cervix

Your doctor will consider these factors when interpreting the fFN test results.

Accuracy and Limitations of the fFN Test

While the foetal fibronectin test is a valuable tool for assessing preterm birth risk, it's not perfect. Here's what you should know about foetal fibronectin test accuracy:

• High negative predictive value (NPV): A negative fFN has a 95-99% NPV, meaning it's very reliable for ruling out delivery within 7-14 days. However, it doesn't eliminate the possibility of preterm birth entirely.
• Moderate positive predictive value (PPV): A positive result has a 25-30% PPV for delivery within 1-2 weeks. So while it suggests increased risk, it doesn't guarantee preterm labour.
• Short prediction window: The fFN test is most accurate for predicting delivery within the next 7-14 days. It doesn't provide long-term risk assessment beyond this timeframe.

fFN test results should be considered alongside cervical length, clinical signs, and other risk factors for the most accurate prediction of preterm labour.

Managing Preterm Labor Risk Based on fFN Results

Your personalised management plan depends on your specific fFN test results and clinical scenario.

Typical approaches may include:

• Negative fFN: If you have no other worrisome signs, you'll likely continue your usual prenatal care and be vigilant for preterm labour symptoms. Retesting in 1-2 weeks may be advised.
• Positive fFN: Depending on your symptoms and cervical exam, your doctor may recommend hospitalisation, close monitoring, medications (like corticosteroids and tocolytics), and possible transfer to a hospital with NICU capabilities.

Conclusion: Should You Consider the fFN Test?

If you're experiencing symptoms of preterm labour or have risk factors for preterm birth, the foetal fibronectin test can provide valuable information to guide your care. By predicting the likelihood of delivery in the near term, the test helps you and your healthcare team make informed decisions about management, potentially avoiding unnecessary interventions while ensuring appropriate care for those at higher risk.

At Metropolis Healthcare, we understand the challenges surrounding pregnancy complications like preterm labour. Our team of skilled technicians provides reliable fFN test services with the convenience of at-home sample collection. We deliver accurate results promptly, empowering you and your doctor with the insights needed to optimise your prenatal care. If you have questions about the foetal fibronectin test cost or procedure, our experts are here to help.

FAQs

What is fibronectin positive in pregnancy?

A positive fFN test in pregnancy means that foetal fibronectin protein is detected in vaginal fluid between 22-35 weeks gestation. This suggests an increased risk of preterm labour and delivery.

How do you collect foetal fibronectin?

To collect a sample for foetal fibronectin testing, a cotton-tipped swab is inserted into the vagina and gently rubbed against the cervix or posterior vaginal wall to obtain a sample of cervicovaginal secretions. The swab is then sent to a laboratory for analysis.

How accurate is positive foetal fibronectin?

A positive fFN test result moderately predicts delivery within 1-2 weeks (25-30%). It indicates increased preterm labour risk but isn’t certain, as false positives can result from contamination or other factors.

Is the fFN test painful?

Most women do not find the fFN test procedure painful. You may feel some discomfort or pressure similar to a Pap smear when the speculum is inserted and the swab is collected, but it only takes a few seconds.

Can the fFN test prevent preterm labour?

The fFN test itself does not prevent preterm labour, but it allows for identification of high-risk women. This guides interventions like steroids and tocolytics that can prolong pregnancy and improve neonatal outcomes.

Is the test safe for me and my baby?

Yes, the foetal fibronectin test is very safe for both mother and baby. It's a non-invasive vaginal swab test that does not pose any known risks. The procedure only takes a few minutes.

What does a negative test result mean?

A negative fFN test result is highly reassuring. It means you have less than a 1% chance of going into labour within the next 2 weeks. In most cases, a "watchful waiting" approach is appropriate.

How long after positive foetal fibronectin do women deliver?

Women typically deliver within 1-2 weeks after a positive foetal fibronectin test, but only about 25-30% do. Many may deliver later or carry to term despite the positive result.

What causes false-positive foetal fibronectin?

False-positive fFN results can occur due to factors like recent sex, vaginal infections, bleeding, lubricants, medications, or cervical procedures. Doctors consider these when interpreting the test accurately.

Are there any risks or side effects of the test?

The fFN test is safe with no known risks. Minor discomfort and rare light spotting may occur during swab collection, similar to a Pap smear, but there are no long-term side effects.