A 28-year-old multigravida with a favorable cervix (Bishop score 9) at 40 weeks of gestation requires induction of labor for mild preeclampsia without severe features. Which is the most common method of induction of labor used in this clinical scenario?

Explanation

## Induction of Labor in Favorable Cervix **Key Point:** Oxytocin infusion is the most common and preferred method of labor induction when the cervix is favorable (Bishop score ≥8). ### Clinical Context In this case: - Bishop score is 9 (favorable) - Cervical ripening is NOT needed - Direct induction with oxytocin is appropriate ### Oxytocin for Labor Induction #### Mechanism of Action 1. Binds to oxytocin receptors on myometrial smooth muscle 2. Increases intracellular calcium 3. Stimulates uterine contractions 4. Increases frequency and intensity of contractions over time #### Dosing Protocol (Standard) - **Starting dose:** 0.5–1 mIU/min IV infusion - **Increment:** Increase by 1–2 mIU/min every 30–40 minutes - **Maximum dose:** Usually 20 mIU/min (some protocols go up to 40 mIU/min) - **Goal:** Achieve 3–5 contractions in 10 minutes, each lasting 40–60 seconds **High-Yield:** The "rule of 3s" for adequate labor: 3 contractions per 10 minutes, each lasting 30+ seconds, with adequate intensity. ### When to Use Oxytocin vs. Prostaglandins | Scenario | Agent | Reason | |----------|-------|--------| | **Favorable cervix** | Oxytocin | Direct induction; ripening not needed | | **Unfavorable cervix** | Misoprostol/Dinoprostone | Cervical ripening required first | | **Multiparous woman** | Oxytocin (preferred) | Better response; lower uterine rupture risk | | **Primigravida** | Oxytocin or prostaglandins | Both acceptable; depends on cervical status | | **Prior uterine scar** | Oxytocin (caution) | Avoid prostaglandins due to rupture risk | **Clinical Pearl:** In multiparous women with favorable cervices, oxytocin induction has the highest success rate and is the most commonly used method in clinical practice. ### Contraindications to Oxytocin Induction - Placenta previa - Vasa previa - Cord presentation - Active genital herpes (relative) - Prior classical cesarean section (relative) **Warning:** Prostaglandins (misoprostol, dinoprostone) are NOT first-line when the cervix is already favorable—they increase the risk of hyperstimulation and tachysystole without additional benefit.