How Accurate Is It?
A negative fetal fibronectin test result means that delivery is not imminent. In fact, a woman with a negative test will deliver in the next 14 days less than one percent of the time. If a woman tests negative for the presence of fFN protein, she can be assured that she will almost certainly not deliver within the next 7 to 14 days.
A positive fFN test result, however, does not necessarily mean that a woman will delivery early. Fetal fibronectin protein is always present before preterm delivery, but imminent preterm delivery is not the only cause of detectable levels of fFN protein. A positive test means the woman should be monitored more closely, and her health care provider will use it as only one factor in making treatment decisions.
False positive tests can be caused by anything that disturbs the cervix or uterus. These can include a pelvic exam or sexual intercourse within the previous 24 hours. Lotions, soaps, and douches can interfere with fFN levels, and male seminal fluid can contain fFN protein. Women scheduled for an fFN test should have neither intercourse nor a pelvic exam for a day or two before the test.
If these guidelines are followed, an inaccurate result can still occur due to human error. Cotton swabs and glass containers can cause false negative results.