Fetal fibronectin (fFN) is used to test pregnant women who are between 22 weeks and 35 weeks of gestation and are having symptoms of premature labor. The test helps predict the likelihood of premature delivery.
Many pregnant women experience symptoms that suggest preterm labor. These may include uterine contractions, changes in vaginal discharge, backaches, pelvic pressure, cramping, and cervical dilation. However, not all symptomatic women will actually have a preterm delivery. The majority will go on to deliver at term.
Unfortunately, while premature births can have successful endings, serious complications are possible when a baby leaves the womb early. Babies who are less than 37 weeks old frequently have difficulty breathing and feeding. Their lungs and other organs are immature and do not function normally, and the strain on them can cause persistent health problems. The more premature the newborn, the more likely it is that he or she will experience complications.
If a health practitioner thinks that a woman might deliver early, she will consider treatments designed to delay delivery. These treatments can have unwanted side effects, however, so, knowing whether or not a woman is likely to deliver prematurely helps in the decision on the best course of action. The fFN test is a relatively noninvasive tool that can help distinguish between those women who are likely to deliver shortly and those who are not.
The fFN test should only be used for those who:
Have intact amniotic membranes
Have a cervix that has not dilated more than 3 centimeters
Have only slight vaginal bleeding
Do not have cervical cerclage (a cervix that has been sewn shut during pregnancy to help keep the baby in the uterus; used when someone has a weak cervix)
The fFN test is not recommended for screening asymptomatic, low-risk women.
The fFN test is ordered when a woman is 22 weeks to 35 weeks pregnant and has symptoms of preterm labor. These may include uterine contractions, a change in vaginal discharge, backache, abdominal discomfort, pelvic pressure, and/or cramping.
The fFN test may be repeated after 2 weeks if the first fFN is negative and labor symptoms persist beyond the next 7 to 14 days. The test may therefore be repeated several times since each test result is valid for the following 7 to 14 days.
The fFN test is not meant to be used for women with placental abruption (premature detachment of the placenta), premature rupture of membranes, placenta previa (a placenta attached to the lower portion of the uterus), or moderate to heavy vaginal bleeding.
A positive fFN result is not very predictive of preterm labor and delivery. However, a negative fFN result is highly predictive that preterm delivery will not occur within the next 2 weeks.
In other words, when the fFN test is performed on a symptomatic woman who meets the qualifying conditions, a negative test result means that there is a less than 1% chance of her having a premature delivery within the next 2 weeks. A health practitioner will also use other tests and her clinical expertise to evaluate each individual situation.
Since there are risks associated with treating a woman for premature labor (in anticipation of a premature delivery), a negative fFN can reduce unnecessary hospitalizations and drug therapies.
A positive fetal fibronectin test is less specific. It is associated with an increased risk for preterm delivery and with neonatal complications, but it will not tell a woman's health care provider whether or not she will deliver early. A positive test suggests the need to monitor a symptomatic woman more closely.
If the risk for preterm delivery is high, extra measures can be taken to delay delivery for as long as possible and to help prepare the fetus for birth. Tocolytic agents can be used to help inhibit uterine contractions, the hormone progesterone can help to reduce the incidence of preterm birth in women who have a history of preterm births, and corticosteroids can be given to the woman to help mature the baby's lungs. In addition, the woman may be put on bedrest or hospitalized and may be transferred to a medical institution that has the expertise and equipment to handle premature births.
This article was last reviewed on November 19, 2013. | This article was last modified on April 27, 2015.
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