What is the rate of failure of induction with dinoprostone (prostaglandin E2) gel?

Rate of Failure of Induction with Dinoprostone Gel

The failure rate of labor induction with dinoprostone gel ranges from 1.2% to 10.8%, with significantly better outcomes in multiparous women compared to nulliparous women.

Evidence from Clinical Trials

Overall Failure Rates

• In a randomized controlled trial comparing dinoprostone gel to vaginal tablets, the failed induction rate requiring cesarean delivery was 1.22% for the gel formulation 1
• When comparing dinoprostone vaginal tablets to gel in the same study, tablets had a significantly higher failure rate of 10.84% versus 1.22% for gel (P = 0.01) 1
• These differences were primarily driven by outcomes in primigravid women, where the gel demonstrated superior efficacy 1

FDA-Approved Dinoprostone Insert Data

• In three randomized, double-blind, placebo-controlled trials evaluating the dinoprostone vaginal insert (CERVIDIL), treatment success rates (defined as vaginal delivery within 12 hours, Bishop score ≥6, or ≥3 point increase in Bishop score) ranged from 55% to 87% depending on parity 2
• For nulliparous women, success rates were 65-72% with dinoprostone insert versus 24-48% with placebo 2
• For multiparous women, success rates were 55-87% with dinoprostone insert versus 24-41% with placebo 2

Key Factors Influencing Failure Risk

Maternal Age

• Maternal age is an independent significant variable determining risk of cesarean delivery (p = 0.01, OR 1.08), which serves as a proxy for induction failure 3

Parity Status

• Nulliparous women have substantially higher failure rates than multiparous women across all dinoprostone formulations 1
• The efficacy differences between gel and tablet formulations were only statistically significant in primigravid women 1

Medical Comorbidities

• Patients with mild preeclampsia have a three times higher risk for cesarean section, indicating higher induction failure rates 3

Management After Initial Dinoprostone Failure

Second-Line Prostaglandin Options

• When dinoprostone vaginal insert fails, a second induction cycle can be attempted with either dinoprostone vaginal gel or oral misoprostol 4
• Overall success rates after failed dinoprostone insert: 70.6% achieved active labor and 62.4% had vaginal delivery with repeat prostaglandin administration 4
• Dinoprostone vaginal gel as second-line achieved active labor in 69.6% and vaginal delivery in 62.5% of patients 4
• Oral misoprostol as second-line achieved active labor in 71.7% and vaginal delivery in 62.3% of patients 4
• No significant difference in efficacy between these two second-line options (P = 0.83 for active labor, P = 0.99 for vaginal delivery) 4

Critical Safety Considerations

Absolute Contraindications

• Dinoprostone is absolutely contraindicated in women with active cardiovascular disease due to profound effects on blood pressure, theoretical risk of coronary vasospasm, and risk of arrhythmias 5
• Dinoprostone should be avoided in women with severe aortic stenosis, pulmonary hypertension, or cyanotic heart disease 5

Prior Cesarean Section

• While some centers use dinoprostone in women with prior cesarean section, uterine rupture occurred in 4.3% of TOLAC patients induced with PGE2 in one prospective study 6
• The cesarean section rate in TOLAC patients induced with dinoprostone was 44.7% versus 31.6% in women without prior cesarean 6

Comparative Efficacy: Pessary vs. Gel

• The 24-hour dinoprostone vaginal pessary achieved a significantly higher rate of spontaneous vaginal delivery (72%) compared to repeat-dose dinoprostone gel (54%) in women with Bishop score ≤4 7
• The pessary formulation resulted in lower operative vaginal delivery rates (3% vs. 15%) 7
• Cesarean section rates were 25% with pessary versus 31% with gel, though this difference did not reach statistical significance 7

Common Pitfalls to Avoid

• Do not assume all dinoprostone formulations have equivalent efficacy: gel formulations demonstrate superior outcomes compared to tablets, particularly in nulliparous women 1
• Do not prematurely classify induction as failed: consider a second cycle of prostaglandin administration, which achieves vaginal delivery in approximately 62% of cases 4
• Do not overlook maternal age as a risk factor: each year of increasing maternal age incrementally increases cesarean risk 3