Fetal fibronectin (fFN) is a

fibronectin Fibronectin is a high- molecular weight (~500-~600 kDa) glycoprotein of the extracellular matrix that binds to membrane-spanning receptor proteins called integrins. Fibronectin also binds to other extracellular matrix proteins such as col ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

produced by

fetal A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic stage, the fetal stage of development takes place. Prenatal development is a ...

cells Cell most often refers to: * Cell (biology), the functional basic unit of life * Cellphone, a phone connected to a cellular network * Clandestine cell, a penetration-resistant form of a secret or outlawed organization * Electrochemical cell, a d ...

. It is found at the interface of the

chorion The chorion is the outermost fetal membrane around the embryo in mammals, birds and reptiles (amniotes). It is also present around the embryo of other animals, like insects and molluscs. Structure In humans and other therian mammals, the cho ...

and the

decidua The decidua is the modified mucosal lining of the uterus (that is, modified endometrium) that forms every month, in preparation for pregnancy. It is shed off each month when there is no fertilized egg to support. The decidua is under the influe ...

(between the fetal sac and the

uterine lining The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The functional layer ...

). Fetal fibronectin is found normally in vaginal fluid in early pregnancy prior to 22 weeks due to normal growth and development of tissues at the junction of the uterus and amniotic sac. It may also be found in vaginal fluid after 36 weeks as labor approaches. However, fFN should not be detected between 22 and 36 weeks. It can be thought of as an adhesive or "biological glue" that binds the fetal sac to the uterine lining. It is the product of

alternative splicing Alternative splicing, alternative RNA splicing, or differential splicing, is an alternative RNA splicing, splicing process during gene expression that allows a single gene to produce different splice variants. For example, some exons of a gene ma ...

of the fibronectin gene and contains a oncofetal domain not present in adult fibronectin.

Screening test

Fetal fibronectin "leaks" into the

vagina In mammals and other animals, the vagina (: vaginas or vaginae) is the elastic, muscular sex organ, reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The #Vag ...

if a preterm delivery is likely to occur and can be measured in a

screening test In medicine, screening is a strategy used to look for as-yet-unrecognised conditions or risk markers. This testing can be applied to individuals or to a whole population without symptoms or signs of the disease being screened. Screening interv ...

. Testing will produce a negative or a positive result. A positive result indicates that fetal fibronectin is present in the cervical secretions. A positive result between 22 and 34 weeks gestation signals an increased risk of preterm birth within the next 7 days. A negative result indicates that there is not fetal fibronectin in the cervical secretions. Fetal fibronectin testing has poor specificity (64%) and positive predictive value (10%). Because of this, the American College of Obstetricians and Gynecologists does not consider positive fFN as diagnostic of prelabor rupture of membranes in the absence of other signs and symptoms and cautions that "these test kits should be considered ancillary to standard methods of diagnosis." While the specificity and positive predictive value are poor, fetal fibronectin testing has excellent sensitivity (100%) and negative predictive value (100%). Therefore, a negative fFN test is a very strong indicator that preterm birth is not likely to occur within the next 7 days. A 2019 Cochrane Review found that while management based on the results of fFN appeared to reduce preterm birth before 37 weeks, the quality of evidence was low. The test is easily performed and is usually painless. A specimen is collected from the patient using a vaginal swab. The swab is placed in a transport tube and sent to a laboratory for testing. Most labs can easily produce a result in less than one hour. At or after 22 weeks of gestation, fFN levels greater than or equal to 50 ng/mL are associated with an increased risk of spontaneous preterm birth. A false positive fetal fibronectin result can occur if the test is performed after digital examination of the cervix or after having had intercourse. It is important that the swab be taken before a digital cervical examination or more than 24 hours following intercourse or previous examination.

References

External links

Fibronectin Test
- FibronectinTest.co.uk {{DEFAULTSORT:Fetal Fibronectin Embryology Tests during pregnancy de:Fibronektin#Fetales Fibronektin

Screening test

See also

References

External links