Fetal Fibronectin (fFN) Test

A fFN test by Hologic is a safe, reliable, non-invasive test (similar to a Pap test) that can help your doctor tell if your body may be getting ready for delivery, even before you feel any of the symptoms. If you are between 22-34 weeks pregnant, fetal fibronectin testing can help predict your risk for preterm delivery. fFN testing is approved for use in women from weeks 22 to 35 of pregnancy. Your doctor or nurse-midwife can determine whether it will be useful in your situation, so talk with your doctor or nurse-midwife about the test, your risk for premature birth, and if getting the test makes sense for you.

It is a simple, non-invasive vaginal swab test that can be given in our clinic. Even better it can be combined with a transvaginal Cervical Scan to assess cervical incompetence – a known leading casue of preterm labour. fFN can often be detected before other symptoms of preterm labor, such as contractions and changes in cervical length. Doctors may use a combination of signs and symptoms and tests when deciding the best course of action to take in relation to your pregnancy.

The test cannot be done however if the patient has had sexual intercourse within 24 hours prior to sampling; moderate or gross vaginal bleeding; advanced cervical dilation (3 cm or greater); rupture of membranes; gestational age <22 weeks or >35 weeks; or suspected or known placental abruption or placenta previa.

What is Fetal Fibronectin?

Fetal fibronectin (also known as fFN) is a “glue-like” protein that bonds your developing baby to your uterus. Fetal fibronectin is detectable in vaginal secretions in the very beginning of pregnancy, when this bond is first forming, and then again at the end of pregnancy, when your body is getting ready to deliver your baby.

How does the test work?

fFN is a special protein that literally holds your baby in place in the womb. After the 35th week of pregnancy, it begins to break down naturally, and is detectable. If your body is getting ready to give birth prematurely, fFN may be detected before week 35. Fetal fibronectin is a “glue-like” protein that holds the developing baby in the womb.

How much Fetal Fibronectin is normal?

From weeks 22 to 35 in your pregnancy, there should be very little fFN detectable and therefore detection of fFN could be a sign that your body is getting ready to go into labor prematurely.

Women with a NEGATIVE fetal fibronectin test result

Approximately 99.2% of women with symptoms of preterm labor who have a negative test result will not deliver within the next two weeks. Less than 1% of women will deliver before 28 weeks if they have a negative fetal fibronectin test result at 22 to 24 weeks. In a woman at risk with symptoms of preterm labor, a test result that is negative provides 99.2% assurance that she will not deliver in the next two weeks.

This helps make it possible to:

  • Alleviate patient uncertainty
  • Avoid unnecessary hospitalization, testing, and extended maternity leave
  • Reduce or eliminate unnecessary interventions
  • Provide important education regarding symptoms
  • Reassure patients that they have less than a 1% chance of delivery within the next 14 days1
  • Reduce or eliminate costs associated with hospital admissions and transportation
  • A physician may wish to monitor the patient’s fFN test results at her office visits. fFN tests, can be given as often as biweekly, from weeks 22 to 35, in order to monitor the presence of fetal fibronectin.

Women with a POSITIVE Fibronectin Test result

Women with symptons: Over 40% of women with symptoms of preterm labor who have a positive test result will deliver prematurely (before 37 weeks of gestation). A woman who tests positive at 22 to 24 weeks is nearly 60 times more likely to deliver within the next 4 weeks, compared with a woman with a negative test result. Management plans may include closer surveillance, reduced daily activity, and treatment options.

Women with no symptoms: Women at risk with no symptoms of preterm labor were nearly 60 times more likely to deliver within 4 weeks after a positive test result at 24 weeks than women with a negative test result.

In the NIH Preterm Prediction Study, fFN testing detected nearly two-thirds of the preterm births that occured prior to 28 weeks

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Risk factors for premature delivery

You may be at risk if you have one of the following risk factors:

  • Symptoms of preterm labor – These include contractions every 10 minutes or more often, change in vaginal discharge, pelvic pressure, backache, menstrual-like cramps, or abdominal cramps with or without diarrhea.
  • A prior preterm birth – If you’ve already delivered a baby early (before 37 weeks), or if you’ve experienced preterm labor in a prior pregnancy, you have an increased risk of delivering early again
  • Cervical abnormalities – If you have cervical abnormalities as a result of surgery or as detected by your doctor during ultrasound, you may be at increased risk of delivering your baby early.
  • Twins or triplets – If you are carrying twins or triplets, the added weight and pressure of multiple babies can lead to an early delivery.

Most women who get tested, will have a negative test result, which can give them great “peace of mind” — a negative test result means you can be 99.2% assured that you won’t go into labor in the next two weeks. On the other hand, if you get a positive test result, that does not always mean your baby will be born preterm.

Advice for pregnant women with no risk factors

Even if you don’t have any risk factors, you should contact your healthcare provider if you have any symptoms of preterm labor, which can include: • Contractions (your abdomen tightens like a fist) every 10 minutes or more often

• Change in vaginal discharge (leaking fluid or bleeding from the vagina)

• Pelvic pressure (the feeling that your baby is pushing downward)

• Low, dull backache

• Cramps that feel like your period

• Abdominal cramps with or without diarrhea

What the experts say

Among the existing risk factors for preterm birth, fFN is the most powerful independent predictor of preterm birth <32 weeks, even more so than prior preterm birth or cervical length.

In the NIH Preterm Prediction Study of 2929 pregnant women, fFN testing predicted almost two-thirds of the spontaneous preterm births at less than 28 weeks.2 In a study of symptomatic women, 99.2% of women with negative fetal fibronectin test results did not deliver in the next 14 days.3

Clinicians from throughout the country are discovering the benefits of fetal fibronectin. Here’s what a few of them had to say about the test’s usefulness, and how it compares to other methods of assessing preterm labor risk.

Kathryn Shaw, MD, is a perinatologist at White Memorial Medical Center in Los Angeles. She finds fFN testing to be “far superior” to other methods of assessing the risk of preterm delivery. This test has been very useful in identifying patients who are not at risk for preterm birth, and thus allows for less intervention and less disruption of those patients’ lives. It also allows for more timely intervention, based on a positive fFN result, when clinical symptoms are minimal.

Thomas A. Raskauskas, MD, of the North Shore Medical Center in Salem, Massachusetts, finds fFN testing to be “the best method to date” for assessing preterm delivery risk. He tests asymptomatic women with a history of preterm birth or other risk factors for PTB. A woman who had two normal term deliveries presented at 31 weeks with contractions. Her initial fFN test was negative, and a repeat test one week later also was negative. The patient, who was the breadwinner of her family, returned to work one week after the initial evaluation, and is still pregnant at 37 weeks. Because of the reassurance provided by the negative results, she was able to retain her full salary, without losing her maternity benefits.

John M. Thorp, Jr, MD, is a perinatologist and professor of obstetrics and gynecology at the University of North Carolina School of Medicine. The majority of his patients are high risk. Dr. Thorp relies on the high negative predictive value of a fFN test to avoid unnecessary treatment of preterm labor symptoms. He finds the test to be “superior to clinical judgment. Dr. Thorp recalls a patient who was reluctant to become pregnant again due to preterm uterine activity in a previous pregnancy, and who did not want to be “sentenced” to bed rest again. Using the negative predictive value, we were able to avoid unnecessary treatments for her uterine activity, and she was able not only to work until term, but also to care for her child.

Daniel Eller, MD, uses fFN testing in his urban, maternal-fetal medicine practice in Atlanta, Georgia. He tests hospitalized patients with shortened cervices or symptoms of preterm labor and outpatients with shortened cervices or other risk factors for PTD. fFN helps him determine which patients need to be hospitalized and for how long. He says that a negative test result allows him to be less aggressive with tocolytics and hospitalization than he otherwise would be. Dr. Eller’s patients reap the benefits when they avoid weeks or even months of hospitalization by virtue of testing negative. Of one patient in particular, he says: I know she appreciated being home with her family, and she said the negative results gave her a sense of security. In addition, the cost of her maternity care was significantly reduced.”