Cervical assessment.

The relationship between the clinical state of the cervix and spontaneous onset of labor has long been known. The cervix can be characterized by evaluating five parameters: effacement, dilatation, firmness, position, and level of the presenting part. The relative associations between successful labor induction and these factors appears to vary, with the strongest correlation observed with cervical dilation, whereas the association with cervical station and position is less robust. By its nature, cervical examination is somewhat subjective, but the use of objective criteria and numerical scoring of this information has substantially reduced this source of error. The Bishop score and it variations have been used widely and accepted in clinical practice. Its advantage lies in its simplicity, reproducibility, and predictability in successful inductions. Although criticized for the equal weight given to each of the five elements, none of the modifications to the original score has been shown to improve predictability. Although the Bishop score was initially evaluated only in multiparous women, it has been extended to nulliparous women with an equal degree of predictive value. To date, the Bishop score remains as the best and simplest method available to determine the duration and safety of induced labor.