fetal fibronectin and spontaneous preterm birth

Last edited 08/2019 and last reviewed 07/2020

  • fetal fibronectin is a glycoprotein that, when absent in cervicovaginal secretions between 24-34 weeks gestation, indicates that a woman is unlikely to give birth within the next 7-14 day (1)
    • test, using a vaginal swab, is easy to perform and test results are rapidly available


  • fetal fibronectin
    • presence of fetal fibronectin is an effective biochemical marker for predicting preterm birth
    • a stable glycoprotein produced by the fetal membranes, adheres the fetal membranes and placenta to the uterine lining and plays a critical role in facilitating the physiological separation of the placenta from the uterus after delivery
    • generally not present at levels >50 ng/mL between 16 and 22 weeks of gestation, earlier studies have shown that its presence (>50 ng/mL) in the cervix or vagina from 22 weeks of gestation and beyond is a powerful predictor of subsequent spontaneous preterm birth (2,3)

  • NICE state (4)
    • fetal fibronectin testing should be considered as a diagnostic test to determine likelihood of birth within 48 hours for women who are 30+0 weeks pregnant or more if transvaginal ultrasound measurement of cervical length is indicated but is not available or not acceptable. Act on the results as follows:
      • if fetal fibronectin testing is negative (concentration 50 ng/ml or less), explain to the woman that it is unlikely that she is in preterm labour and:
        • think about alternative diagnoses
        • discuss with her the benefits and risks of going home compared with continued monitoring and treatment in hospital
        • advise her that if she does decide to go home, she should return if symptoms suggestive of preterm labour persist or recur
      • if fetal fibronectin testing is positive (concentration more than 50 ng/ml), view the woman as being in diagnosed preterm labour and offer treatment measures for preterm labour (tocolysis, maternal corticosteroids)