How is it used?
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 baby, the more likely that they will experience complications.
If your doctor thinks that you might deliver early, he will consider treatments designed to delay delivery. These treatments can have unwanted side effects. So, knowing whether or not a woman is likely to deliver prematurely helps the doctor decide on the best course of action. The fFN test is a relatively noninvasive tool to help the doctor to distinguish between those who are likely to deliver shortly and those who are not.
Fetal fibronectin is used to test pregnant women who are between 22 weeks and 34 weeks of gestation and are having symptoms of premature labor. The test helps predict the likelihood of premature delivery.
The fetal fibronectin test should only be used on 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)
Sexual intercourse or a pelvic examination within 24 hours of testing for fFN can give a
false positive test result.
The fFN test is not recommended for screening asymptomatic patients, even if they are considered to be at high risk for premature labor and delivery.
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When is it ordered?
The fFN is ordered when a woman is 22 weeks to 34 weeks pregnant and has one or more symptoms that may predict preterm labor. These symptoms may include: uterine contractions, a change in vaginal discharge, backache, abdominal discomfort, pelvic pressure, and/or cramping.
The fFN may be repeated after 14 days if the first fFN is negative and labor symptoms persist beyond the next 7-14 days. The test may thus be repeated several times since each test result is valid for the following 7 to 14 days.
The fFN should only be ordered when a woman is symptomatic and meets the qualifying conditions.
The fFN test is not meant to be used on women with more than one fetus (twins, multiples) or on those 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.
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What does the test result mean?
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 7-14 days.
In other words, when the fFN test is done on a symptomatic woman who meets the qualifying conditions, a negative test result means that there is a less than 1% chance of having a premature delivery within the next 7 to 14 days. The doctor will also use other tests and his 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 doctor whether or not she will deliver early. A positive test suggests the need to monitor a symptomatic woman more closely.
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Is there anything else I should know?
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 (a variety of drugs) can be used to help inhibit uterine contractions, and corticosteroids can be given to the woman to help mature the babys lungs; both of these therapies have associated risks. In addition, the woman can be transferred to a medical institution that has the expertise and equipment to handle premature births.
Anything that physically disturbs the cervix or uterus has the potential to elevate fFN levels. Cervicovaginal fluid samples should be collected before any physical examinations. Lubricants, lotions, soaps and douches, should be avoided as they may cause interference with the test as may large numbers of red or white blood cells or bacteria.
Semen may contain enough fFN to create a positive test result. Sexual intercourse within 24 hours may lead to a positive fFN, but if the test is performed and is negative, it is a valid result.
fFN binds to cotton swabs and to glass. Collection must be done with a Dacron swab and put into a plastic container or a false negative fFN may result.
Fetal fibronectin may also bind to Candida, a vaginal yeast. If the patient has a vaginal yeast infection, the result may be a false negative.
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