Preinduction sonographic measurement of cervical length in the prediction of successful induction of labor.
BACKGROUND
Induction of labor is carried out in approximately 20% of pregnancies. However, approximately 20% of women having induction of labor end up having a Cesarean delivery. The traditional method of predicting whether an induced labor will result in successful vaginal delivery is based on the preinduction "favorability" of the cervix as assessed by the Bishop score. However, this assessment is subjective and several studies have shown a poor predictive value for the outcome of induction.


OBJECTIVE
To examine the relationship between preinduction sonographically measured cervical length and the Bishop score and to compare the two measurements in the prediction of successful vaginal delivery within 24 h of induction.


METHODS
In this multicenter study, preinduction cervical assessment was undertaken in 240 women with singleton pregnancies at 37-42 weeks of gestation. The Bishop score was assessed by digital examination and the cervical length was measured by transvaginal sonography.


RESULTS
Multiple regression analysis demonstrated that cervical length, Bishop score and parity provided independent contribution in the prediction of the likelihood of delivering vaginally within 24 h. Further examination of the different components of the Bishop score showed that only cervical length provided a significant contribution in the prediction of the likelihood of vaginal delivery within 24 h. In the receiver operating characteristic curves, the best cut-off point for the prediction of successful induction was 28 mm for cervical length and 3 for the Bishop score. However, cervical length appears to be a better predictor than the Bishop score, with a sensitivity of 0.87 and a specificity of 0.71 compared to 0.58 and 0.77, respectively. Similarly, the Kaplan-Meier survival curves indicate that better discriminatory results in the prediction of vaginal delivery within 24 h are achieved using cervical length rather than the Bishop score.


CONCLUSIONS
Transvaginal sonographic measurement of cervical length provides a useful prediction of the likelihood of vaginal delivery within 24 h of induction.
Pandis
G K
GK
Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, Denmark Hill, London SE5 8RX, UK.
Papageorghiou
A T
AT
Ramanathan
V G
VG
Thompson
M O
MO
Nicolaides
K H
KH
D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D036861:Delivery, Obstetric; D005260:Female; D005865:Gestational Age; D006801:Humans; D007751:Labor, Induced; D011237:Predictive Value of Tests; D011247:Pregnancy; D012372:ROC Curve; D012044:Regression Analysis; D013997:Time Factors; D016216:Ultrasonography, Prenatal