Definition

• Induction refers to interventions designed to initiate labor before spontaneous onset with a view to achieving vaginal delivery.
  
• This should be distinguished from augmentation which refers to enhancement of uterine contractility in women in whom labor has already begun.

Patient assessment (Figure 62.1)

• The appropriate timing for induction is the point at which benefit to mother and/or fetus is greater if pregnancy is interrupted than if pregnancy is continued, and depends on gestational age.
  
• Indications and contraindications are detailed in Figure 62.1.

Bishop score

• The success of induction depends in large part on the status of the cervix. In 1964, Bishop designed a cervical scoring system to prevent iatrogenic prematurity. This system has since been modified (Figure 62.1) and used to predict the success rate of induction. If the Bishop score is favorable (defined as ≥6), the likelihood of a successful induction and vaginal delivery is high. If unfavorable (<6), the probability of successful induction is reduced and pre-induction cervical “ripening” (maturation) may be indicated.
  
• Cervical ripening describes a complex series of biochemical events that alter cervical collagen and ground substance composition, resulting in a softer and more pliable cervix. A number of agents are available to facilitate this maturation (Figure 62.1). Potential benefits include fewer failed inductions, shorter hospital stay, lower fetal and maternal morbidity, lower medical costs, and possibly lower cesarean section delivery rates.

Methods (Figure 62.1)

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