A 32-year-old multigravida (G3P2) at 40 weeks + 5 days with a history of one prior vaginal delivery and one prior cesarean section (for cephalopelvic disproportion) presents for induction of labor. Ultrasound shows a cephalic presentation, adequate amniotic fluid, and an estimated fetal weight of 3.2 kg. The cervix is soft, 3 cm dilated, 70% effaced, and the fetus is at −1 station (Bishop score = 7). The patient desires a trial of labor after cesarean (TOLAC). Which agent is most appropriate for cervical ripening in this patient?

Explanation

## Cervical Ripening in TOLAC (Trial of Labor After Cesarean) **Key Point:** In patients with a prior uterine scar (cesarean delivery), mechanical ripening methods (Foley catheter balloon) are preferred over prostaglandins due to the lower risk of uterine rupture and tachysystole. ### Prostaglandin Safety in TOLAC **High-Yield:** Prostaglandins are relatively contraindicated in TOLAC: | Agent | Mechanism | Risk in TOLAC | Status | |-------|-----------|---------------|--------| | **Misoprostol** | PGE₁ analog | Increased uterine tachysystole; uterine rupture risk ~1% | Contraindicated | | **Dinoprostone** | PGE₂ analog | Increased hyperstimulation; rupture risk elevated | Relative contraindication | | **Mechanical (Foley)** | Mechanical dilation | No systemic effect; lower rupture risk | **Preferred** | | **Oxytocin** | Synthetic oxytocin | Safe in TOLAC if used cautiously with fetal monitoring | Acceptable | **Warning:** Misoprostol is explicitly contraindicated in TOLAC by ACOG due to increased rates of uterine rupture. Dinoprostone carries similar concerns, though some centers use it cautiously. ### Mechanical Ripening: Foley Catheter Balloon **Clinical Pearl:** The Foley catheter balloon (or double-balloon catheter) is the safest ripening method in TOLAC: 1. **Mechanism:** Direct mechanical dilation of the cervix without systemic hormonal effects 2. **Technique:** 16–18 Fr Foley catheter inserted transcervically; balloon inflated with 30–60 mL sterile water; gentle traction applied 3. **Duration:** Left in place for 12–24 hours or until expulsion 4. **Advantages:** - No systemic prostaglandin effects - Lower risk of uterine hyperstimulation - Can be removed immediately if complications arise - Reversible 5. **Success rate:** ~70% cervical ripening; ~60% vaginal delivery after ripening **Mnemonic: TOLAC = Traction Over Latex And Catheter** — Mechanical methods are safest in TOLAC. ### Why This Patient Needs Ripening Although the cervix is soft and partially dilated (Bishop = 7, borderline), the patient is post-term (40+5) and requires induction. Mechanical ripening optimizes the cervix while maintaining TOLAC safety. ### Oxytocin Alone: Why Not Ideal Here? While oxytocin is safe in TOLAC, starting with a borderline unfavorable cervix (Bishop 7) without prior ripening increases failure rates. Mechanical ripening first improves success.