Background: Preterm delivery is the leading cause of neonatal mortality in the United States, but efforts to address the problem are hampered by the inability to predict accurately which pregnancies are at risk. We postulated that damage to the fetal membranes may release fetal fibronectin into the cervix and vagina, giving rise to a biochemical marker for preterm delivery.
Methods: We measured fetal-fibronectin concentrations in cervical and vaginal secretions, amniotic fluid, and maternal plasma with a sensitive immunoassay using the monoclonal antibody FDC-6. Immunohistochemical studies were used to determine the distribution of fetal fibronectin in the placenta and amniochorionic membranes and to ascertain its cell of origin.
Results: Women with uncomplicated pregnancies (n = 163) who delivered at term rarely had cervicovaginal fetal-fibronectin concentrations above 0.05 micrograms per milliliter between 21 and 37 weeks of gestation (11 of 267 cervical samples [4 percent] and 9 of 267 vaginal samples [3 percent]. High levels of fetal fibronectin were detected in amniotic fluid and in the cervical or vaginal secretions of 93.8 percent of the women with preterm rupture of membranes (n = 65). Cervical or vaginal fetal fibronectin was also present in 50.4 percent of the women with preterm uterine contractions and intact membranes (n = 117), and its presence identified the women who delivered before term (n = 60) with a sensitivity of 81.7 percent and a specificity of 82.5 percent. In the placenta and membranes, fetal fibronectin was found at points of contact with the uterine wall.
Conclusions: The presence of cervicovaginal fetal fibronectin in the second and third trimesters of pregnancy identifies a subgroup of women who are at high risk for preterm delivery. This phenomenon may reflect the separation of the chorion from the decidual layer of the uterus, with the release of intact or degraded chorionic components of the extracellular matrix into the cervical and vaginal secretions.