To help evaluate a pregnant woman's risk of preterm delivery
Fetal Fibronectin (fFN)
When you are 22 to 35 weeks pregnant and are having symptoms of premature labor; sometimes if you are at high risk, such as if you have had a previous preterm delivery or have a short cervix
A swab is used to take a sample of cervical or vaginal fluid from the posterior portion of the vagina or from the area just outside the opening of the cervix.
Anything that physically disturbs the cervix or uterus has the potential to elevate fFN levels. Therefore, your healthcare practitioner should collect the sample before a pelvic examination or vaginal ultrasound. Semen may contain enough fFN to create a positive test result, so sexual intercourse should be avoided within 24 hours of sample collection. Avoid lubricants, lotions, soaps, and douches at least a day before the test.
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How is it used?
Fetal fibronectin (fFN) is used to test pregnant women who are between 22 weeks and 35 weeks of pregnancy and are having symptoms of premature labor. The test helps predict the likelihood of premature delivery within the next 7-14 days.
The fFN test should only be used for pregnant women who:
- Have intact amniotic membranes
- Have a cervix that has not dilated more than 3 centimeters
- Have only slight vaginal bleeding
- Do not have a cervix that has been sewn shut during pregnancy to help keep the baby in the uterus, a procedure (cervical cerclage) used when someone has a weak cervix
The fFN test is not recommended for screening asymptomatic, low-risk women.
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When is it ordered?
The fFN test may be ordered when a woman is 22 weeks to 35 weeks pregnant and has signs and symptoms of preterm labor. These may include:
- Uterine contractions
- A change in vaginal discharge
- Backache
- Abdominal discomfort
- Pelvic pressure
- Cramping
- Dilation of the cervix
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.
Sometimes the test may be ordered when a pregnant woman is at high risk of preterm labor, for example, if she has had a previous preterm delivery or has a short cervix.
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.
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What does the test result mean?
A positive fFN result is not very good at predicting whether a woman is experiencing 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 pregnant woman who is experiencing signs and symptoms of preterm labor, 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 healthcare practitioner will also use other tests and 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 healthcare provider whether or not she will deliver early. A positive test suggests the need to monitor a symptomatic woman more closely.
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What are the risk factors for preterm labor and delivery?
There are a number of risk factors, but the greatest risk seems to be to women who:
- Have had a previous preterm delivery
- Are pregnant with multiples
- Have a short cervix
Other risk factors include:
- Late or no prenatal care
- Having certain chronic conditions, such as high blood pressure or diabetes
- Having certain problems with the uterus, cervix, or placenta
- Having certain infections during the pregnancy
- Being underweight or overweight before pregnancy, or gaining too little or too much weight during pregnancy
- Smoking, drinking alcohol, or using illicit drugs
- Being the victim of abuse or other stressful events
- Having multiple miscarriages
Maternal age (less than 18 or more than 40 years) and race seem also to be factors, with African American women at significantly higher risk than Caucasian or Hispanic women.
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Why not use the fFN test after 35 weeks?
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Can preterm labor and delivery be prevented?
Generally, no but 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 baby for birth. Drugs (tocolytic agents) can be used to help inhibit uterine contractions and the hormone progesterone can help to reduce the incidence of preterm birth in women who have a history of preterm births. Corticosteroids can be given to the woman to help mature the baby's lungs and help prevent neonatal respiratory distress syndrome (RDS). In addition, the woman may be put on bedrest or hospitalized and may be transferred to a hospital that has the expertise and equipment to handle premature births.
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What other tests are used to help determine the risk of preterm delivery?
Other tests include measurement of cervical length as determined by transvaginal ultrasonography and testing for bacterial vaginosis.
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Is there anything else I should know?