Is dinoprostone (prostaglandin E2) pessary useful for cervical ripening and labor induction?

Dinoprostone Pessary for Cervical Ripening and Labor Induction

Dinoprostone pessary is useful and effective for cervical ripening and labor induction in women with unfavorable cervices at term, but it is contraindicated in women with active cardiovascular disease and should be avoided in favor of mechanical methods in high-risk cardiac patients.

Efficacy for Cervical Ripening

Dinoprostone vaginal insert demonstrates clear effectiveness for cervical ripening in appropriate candidates:

• The controlled-release vaginal insert (10 mg) provides sustained dinoprostone delivery to promote cervical ripening through a single application with a retrieval system that allows immediate removal if complications arise 1
• Intensive dosing regimens (3000 μg three times daily, four hours apart) achieve successful cervical ripening or active labor within 24 hours in 82.4% of primigravidae with unfavorable cervices, compared to 42.9% with once-daily dosing 2
• Both intracervical gel and vaginal pessary formulations achieve comparable rates of successful cervical ripening and vaginal delivery, with no significant differences in effectiveness 3

Critical Cardiovascular Contraindications

The European Society of Cardiology provides explicit warnings about dinoprostone use in cardiac patients:

• Dinoprostone is absolutely contraindicated in women with active cardiovascular disease due to more profound effects on blood pressure than prostaglandin E1 4
• There is a theoretical risk of coronary vasospasm and a low but real risk of arrhythmias with dinoprostone use 4
• Mechanical methods such as Foley catheter are preferable to dinoprostone in patients with cyanotic heart disease, where drops in systemic vascular resistance or blood pressure would be detrimental 4

Safety Profile in Standard-Risk Patients

For women without cardiovascular disease, dinoprostone demonstrates acceptable safety:

• The device is generally well tolerated with a favorable maternal and fetal/neonatal safety profile, though uterine hyperstimulation remains a risk that is rapidly reversible upon removal of the insert 1
• In women with previous cesarean section, dinoprostone achieves 62% vaginal delivery rates with 4% postpartum hemorrhage and 0.7% uterine rupture rates 5
• Intensive dosing causes more pain (68.6% vs 42.9%) but maintains low rates of serious adverse events, with only transient cardiotocographic abnormalities that resolve without intervention 2

Comparison with Alternative Agents

When comparing dinoprostone to misoprostol for labor induction:

• Oral misoprostol (20-25 μg every 2-6 hours) results in fewer cesarean sections compared to vaginal dinoprostone (RR 0.84) and has significantly lower costs ($0.36-$1.20 per tablet vs $165 for dinoprostone insert) 6
• Dinoprostone requires refrigeration while misoprostol is stable at room temperature, making misoprostol more practical in resource-limited settings 6

Clinical Pitfalls to Avoid

• Do not administer a second dinoprostone pessary if the first fails after 24 hours—this approach shows no superiority over oxytocin and results in significantly more cervical ripening failure (57.1% vs 19%), longer time to delivery (28.1h vs 9.7h), and trends toward worse neonatal outcomes 7
• Avoid dinoprostone entirely in any woman with active cardiovascular disease, including severe aortic stenosis, pulmonary hypertension, or cyanotic heart disease 4
• Maintain close fetal surveillance during dinoprostone use, particularly in pregnancies with oligohydramnios where transient cardiotocographic abnormalities may occur 2

Pharmacologic Mechanism

• Dinoprostone stimulates myometrial contractions similar to term labor and initiates cervical softening through collagen degradation from collagenase secretion 8
• The drug is rapidly absorbed with peak metabolite levels at 0.5-0.75 hours, completely metabolized in lungs, liver, and kidneys, with renal elimination 8