The fetal fibronectin test compares favorably with other tests for preterm labor. Mild elevation of maternal C-reactive protein, an acutephase reactant, has been reported to correlate with likelihood of delivery within 7 days.“-’ In these studies 63% to 85% of women treated for preterm labor whose C-reactive protein level was 20.8 mgidl were delivered within 1 week of presentation compared with only 6% to 29% of women whose C-reactive protein level was ~0.8 mg/dl. Unlike fetal fibronectin, C-reactive protein is not specific for labor and may be increased with any inflammatory condition. Transvaginal cervical ultrasonography has also been recently described as a method offering im- proved diagnosis of preterm labor.9m11 Ultrasonography was substantially better than digital examination in these studies in predicting preterm birth in women treated for preterm labor. However, transvaginal ultra- sonographic measurement of cervical length is limited in its application by operator training and experience and by the availability of appropriate endovaginal probes. Transabdominal imaging of the cervix is not possible in many women, and when it is obtained it is often inaccurate because of pressure on the cervix from
the requisite large maternal bladder. In contrast, the cervicovaginal fetal fibronectin swab may be easily obtained by a nurse or physician, and the assay may be readily performed in any hospital laboratory.