Procedure & Accuracy of Fetal Fibronectin Testing

Submitted on March 27, 2012

Fetal Fibronectin Testing

Fetal fibronectin testing is carried out to check if a pregnant woman is at risk for a pre term delivery. It is usually performed on women who are between 24 and 34 weeks pregnant and show signs of pre term labor such as contractions, vaginal spotting or bleeding, low back pain, pelvic pain, or a watery vaginal discharge. Women who are at high risk for pre term labor but have no symptoms are tested as well.

Accuracy of the Test

The fetal fibronectin test can predict with some accuracy if a woman is about to go into labor or not. The test looks for fetal fibronectin (fFN) which is a protein that connects the fetal sac to the inside lining of the uterus. It is often thought of as the glue that binds the amniotic sac to the uterus lining. It is usually found in large amounts at the early stages of pregnancy and towards the end when a woman is going into labor. If fFN leaks and shows up in the vagina between 22 and 34 weeks, it could be a sign of premature labor.

Positive Fetal Fibronectin Test

A positive fetal fibronectin test means that fetal fibronectin is present, and if this is between 24 and 34 weeks the woman is at risk of preterm labor. A positive result is however inconclusive; as while a woman could go in to preterm labor soon, she may not go into labor for weeks. A positive result would also require that the doctor prescribe medication or the patient takes complete bed rest to prevent this from happening. Steroid injections could also be given to help the baby’s lungs to develop. A positive result means that there is a chance of delivery sometime before 35 weeks of pregnancy and a 16 % chance of giving birth in the next week itself.

Negative Fetal Fibronectin Test

A negative fetal fibronectin test means that there is no fetal fibronectin present. The pregnancy will continue for at least another week or two and the doctor will not have to prescribe any medication as mentioned above to prevent labor or to help the baby develop.


The fibronectin test is painless. Samples of cervical and vaginal secretions are taken during the test. Most laboratories can give the results in about an hour. There is no risk of miscarriage involved with this test.  Avoid having sex 24 hours before the test. A false positive result can occur if fetal fibronectin testing is carried out after a digital vaginal exam or after intercourse.