['The purpose of this study was to investigate the changes in the level of fetal fibronectin in amniotic fluid during the course of pregnancy.', 'Amniotic fluid samples were obtained from 74 women whose pregnancies ranged in gestation from 14 to 38 weeks. Fetal fibronectin in amniotic fluid was examined with a sensitive immunoassay using a monoclonal antibody FDC-6 which recognizes a unique epitope (III-CS) of the molecule.', 'Fetal fibronectin levels in amniotic fluid decreased significantly during pregnancy (r = -0.79, P < 0.0001). The mean levels at less than 20 weeks of gestation were significantly higher than those at 20-29 weeks (P < 0.0001) and at 30 weeks to term (P < 0.0001).'] Does fetal fibronectin concentration in amniotic fluid decrease with advancing gestational age?