The role of ultrasound and fetal fibronectin in predicting the length of induced labor when the cervix is unfavorable.

Abstract

To compare cervical clinical data, ultrasound parameters and fetal fibronectin assessment in the prediction of the duration of induced labor when the cervix is unfavorable. This was a prospective study of 90 pregnant women with a Bishop score </= 5 undergoing labor induction. The Bishop score and its components, parity, cervical ultrasound parameters and fetal fibronectin level were analyzed using Cox's model in order to determine the most predictive factors for the duration of the latent and active phases of labor as well as its total duration. There was a significant correlation between duration of the latent phase and the whole of labor, and digitally assessed cervical dilatation (P = 0.003 and P < 0.001, respectively), parity (P = 0.006 and P < 0.001), the Bishop score (P = 0.019 and P = 0.003) and ultrasound-determined cervical length (P = 0.035 and P = 0.003). The length of the active phase of labor did not correlate with the cervical status. Funneling did not appear to be predictive of the duration of labor and it had a poor correlation with digital cervical dilatation. The length of the latent phase and that of the whole of labor was significantly longer when cervical dilatation was </= 2 cm (P < 0.001 in each case), when women were nulliparous (P = 0.002 and P < 0.001) and when ultrasound cervical length was >/= 27 mm (P = 0.002 and P = 0.005). Cervical dilatation as assessed by digital examination is the best predictor of the duration of the latent phase and of that of the whole of labor. Ultrasound measurement of cervical length is not more accurate at predicting the duration of labor than are clinical data.