Labor Induction

Definition

Labor induction is the medical or mechanical initiation of uterine contractions before the spontaneous onset of labor to achieve vaginal delivery when continuation of pregnancy may pose risks to the mother or fetus.

Epidemiology

• Induction rates vary globally, with 20–30% of deliveries in high-resource settings being induced.
• More common in nulliparous women and in pregnancies beyond term (>41 weeks).
• Indications include maternal or fetal complications such as preeclampsia, diabetes, or intrauterine growth restriction.
• Rates have increased due to better monitoring and evidence-based guidelines.

Etiology

• Medical indications: post-term pregnancy, preeclampsia/eclampsia, gestational diabetes, fetal growth restriction, oligohydramnios, intrauterine fetal demise.
• Elective induction: patient preference or logistic reasons.
• Mechanical or pharmacologic methods used depending on cervical favorability and clinical scenario.
• Contraindications include placenta previa, vasa previa, transverse fetal lie, or previous classical cesarean section.

Pathophysiology

• Induction methods stimulate uterine contractions via prostaglandins, oxytocin, or mechanical cervical dilation.
• Cervical ripening involves collagen degradation, increased water content, and softening to allow dilation.
• Oxytocin stimulates myometrial contraction through receptor-mediated calcium influx.
• Proper coordination of contractions and cervical change is essential for effective labor induction.
• Failure of induction may occur if cervix is unfavorable or if uterine responsiveness is impaired.