About This Test To Tell You If You May Be Going Into Labor Soon
A simple cervical swab test, the results of which can be determined in a hospital lab, can predict with some accuracy whether or not you are about to go into labor. The test looks for the presence of fetal fibronectin, a protein substance that helps connect the amniotic sac to the inside wall of the uterus. Fetal fibronectin is released into the cervix and vagina during labor or in the presence of an infection, when the bond between the placenta and uterine lining breaks down.
There are two primary benefits of the fFN test: to help prevent and prepare for preterm delivery, as well as to avoid unnecessary labor induction when pregnancy runs past your due date.
The FDA (US Food and Drug Administration) approved a test for fFN in August 1998. They stated that the test is "indicated for use in conjunction with other clinical information as an aid to rapidly assess the risk of preterm delivery... when a cerviocovaginal sample is obtained during a routine prenatal visit between 22 weeks, 0 days and 30 weeks, 6 days of gestation in women with a singleton pregnancy."
"The greatest value of this test is not only its ability to help identify those women who may deliver prematurely but more importantly those who will not," says Robert Heise, MD, a Mayo Clinic obstetrician and gynecologist. "By identifying those patients who may deliver prematurely earlier, before significant cervical dilation has occurred, it is possible to administer medications in an attempt to stop the labor process. Even more importantly, we can give the mother medications that will cross to the baby that will mature the baby's lungs thus preventing the major complication of prematurity, inadequately developed lungs.
At the Mayo Clinic, for example, this simple swab test can be performed without discomfort or side effects to a woman with preterm contractions. The result is available generally in two hours. Currently, only a few medical centers have this on-site capability. Most medical centers send the swab away for analysis; it is usually 24 to 28 hours before the results are known.
"The quick availability of the results is very important," says Dr. Heise. "When fetal fibronectin is not present, we can feel safe sending a woman home thus allowing her to get back into her normal routine rather than exposing her to medications, time away from family and work, and the additional problem of increased worry about her pregnancy. Conversely, if the fetal fibronectin is present, we can take appropriate steps necessary to decrease the risk of a premature birth.
How reliable are the results? A study reported in American Journal of Obstetrics and Gynecology (1994 Jul;171(1):1-4) reported that a vaginal fetal fibronectin value greater than or equal to 60 ng/ml at 39 weeks' gestation is predictive of delivery within 10 days, while values less than 60 ng/ml will identify 95% of pregnancies going past 41 weeks' gestation. And a more recent analysis of 27 studies, which appeared in the American Journal of Obstetrics and Gynecology (1999 May; 180(5):1169-76), reported "For the outcomes of delivery within 7, 14, 21, and 28 days, we calculated sensitivity rates of 76%, 68%, 61%, and 43% and specificity rates of 88%, 89%, 91%, and 93%, respectively." The authors concluded, "Among patients with symptoms of preterm labor, cervicovaginal fetal fibronectin appears to be among the most effective predictors of preterm delivery."
So what does this mean to you? Well, if your pregnancy is normal and you and baby are doing well, don't count on your caregiver giving you this test just to give you an answer in the due-date guessing game. Hang in there and click here to read some tips on dealing with the overdue blues.
But if your caregiver is concerned about you going into labor at the wrong time, the fFN test is yet another tool that can be used to help you toward a healthy birth and baby. However, as Dr Heise notes, "If the fetal fibronectin is not present, there is no need for prolonged hospitalization for observation as was the management in the past, and no need for treatment with medications that are expensive and potentially dangerous."