## Cervical Ripening Agents in Labor Induction **Key Point:** Misoprostol is the preferred first-line agent for cervical ripening when the cervix is unfavorable (Bishop score <6) prior to oxytocin-induced labor. ### Why Misoprostol? **High-Yield:** Misoprostol (a prostaglandin E1 analogue) is preferred because it: - Is cost-effective and widely available - Does not require refrigeration (stable at room temperature) - Can be administered vaginally, buccally, or sublingually - Has a rapid onset of action (30 minutes to 2 hours) - Achieves vaginal delivery in 70–80% of cases when used for ripening ### Comparison of Cervical Ripening Agents | Agent | Type | Route | Onset | Cost | Storage | Advantages | | --- | --- | --- | --- | --- | --- | --- | | **Misoprostol** | PGE1 | Vaginal/buccal/sublingual | 30 min–2 hrs | Low | Room temp | First-line, no refrigeration | | Dinoprostone | PGE2 | Vaginal insert | 12–24 hrs | High | Refrigerated | Slower, reversible | | Oxytocin | Synthetic oxytocin | IV | Immediate | Low | Room temp | For labor augmentation, not ripening | | Ergot alkaloids | Ergot derivative | IM/IV | 5–15 min | Low | Room temp | Contraindicated in unfavorable cervix | **Clinical Pearl:** In an unfavorable cervix, oxytocin alone is ineffective and increases the risk of uterine tachysystole and cesarean delivery. Prostaglandins must be used first. **Mnemonic:** **MISO** = **M**isoprostol **I**s **S**tandard **O**pening (for cervical ripening). ### Dosing of Misoprostol for Cervical Ripening - **Vaginal:** 25 mcg every 3–6 hours (maximum 6 doses in 24 hours) - **Buccal/sublingual:** 25 mcg every 3–6 hours - Repeat doses until favorable cervix achieved or labor begins **Warning:** Do not use misoprostol if there is a contraindication to vaginal delivery (e.g., placenta previa, previous classical cesarean section, active genital herpes).
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