A new rapid version of the test for fetal fibronectin (fFN) --an important protein during pregnancy --can help your doctor determine whether those contractions you're feeling are false labor or the beginnings of preterm labor. Early in pregnancy fFN acts like glue, anchoring the placenta and fetal membranes to the uterine wall, explains Charles Lockwood, M.D., professor and chair of the department of obstetrics, gynecology, and reproductive sciences at the Yale University School of Medicine, in New Haven. When it's time for delivery, fFN gets slippery (allowing the fetus and placenta to detach cleanly from the uterus), and can be found in a woman's cervix or vaginal secretions. "Between 22 and 34 weeks, the majority of women who are about to go into preterm labor will have this protein present in their cervix or vaginal mucus," Dr. Lockwood says.
If a woman shows signs of preterm labor, doctors can swab her cervix and/or her vagina --much in the way a Pap test is performed --to check for fFN, and get an accurate sense within an hour of whether these signs are false labor or a warning of the real thing. If no fFN is found, a woman has a less than 5 percent risk of delivering her baby within the next two weeks.
The presence of fFN signals a higher preterm delivery risk and will prompt a doctor to perform other tests, most importantly an ultrasound to measure the length of the cervix. The cervix shortens as delivery approaches, so a short cervix along with a positive fFN test will lead a doctor to take steps to delay delivery, such as prescribing drugs to stop contractions or recommending bed rest. She might also prescribe steroids, which can help mature fetal lungs to make premature birth safer. A long cervix with a positive fFN indicates a lower risk, so a doctor might simply recommend reducing activity or repeating the fFN at a later time.
The new version of the test is a boon for women at risk of preterm labor --those who have delivered prematurely or went into early labor in the past, have uterine or cervical abnormalities, or are pregnant with multiples. Earlier versions of the test took a day or two to provide results, decreasing the window of opportunity to give treatment when preterm labor appeared imminent. The results of the faster test can help determine when it's safe for a woman having contractions to go home and relax, and when it's necessary to intervene to plan for a premature delivery.