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Am Fam Physician. 2022;105(2):193-195

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial relationships.

Key Clinical Issue

What is the effectiveness and what are the harms of cervical ripening methods in the outpatient vs. inpatient setting?

Evidence-Based Answer

There is no significant difference in cesarean delivery rate or fetal harms (e.g., infection) with the use of prostaglandins in the outpatient setting compared with the inpatient setting. (Strength of Recommendation [SOR]: B, inconsistent or limited-quality patient-oriented evidence.) Mechanical methods of cervical ripening in the outpatient setting do not significantly differ from those in the inpatient setting in rates of cesarean delivery, maternal harms (e.g., uterine infection, postpartum hemorrhage), or fetal harms (e.g., birth trauma, shoulder dystocia). (SOR: B, inconsistent or limited-quality patient-oriented evidence.) In the outpatient setting, prostaglandin vs. expectant management, prostaglandin vs. placebo, and dinoprostone vs. membrane sweeping do not differ significantly in cesarean delivery rates, fetal harms, or maternal harms. (SOR: B, inconsistent or limited-quality patient-oriented outcomes.) Mechanical and pharmacologic ripening methods in the outpatient setting have similar cesarean delivery rates.1 (SOR: B, inconsistent or limited-quality patient-oriented outcomes.)

Key questionInterventionFindingsStudiesIncidenceRelative risk (95% CI)I2 for pooled analyses*
Prostaglandin: outpatient vs. inpatientDinoprostoneLow-strength evidence of little or no difference2 RCTs (n = 1,120)23% vs. 23%0.97 (0.75 to 1.25)
DinoprostoneLow-strength evidence of little or no difference4 cohort studies (n = 2,511)33% vs. 33%0.79 (0.67 to 0.98)
Mechanical method: outpatient vs. inpatientSingle-balloon catheterLow-strength evidence of a small, but nonsignificant difference3 RCTs (n = 370)12% vs. 20%0.59 (0.21 to 1.03)
Single-balloon catheterLow-strength evidence of a small, but nonsignificant, difference2 cohort studies (n = 1,057)33% vs. 30%0.95 (0.72 to 1.22)
Outpatient catheter vs. inpatient dinoprostoneLow-strength evidence of a small, but nonsignificant difference2 RCTs (n = 549)33% vs. 26%1.24 (0.88 to 1.70)
Outpatient comparison of methodsDinoprostone gel, 2.5 mg vs. 5.0 mgLow-strength evidence of little or no difference1 RCT (n = 116)20% vs. 19%1.07 (0.51 to 2.22)
Prostaglandin vs. placeboLow-strength evidence of a small, but nonsignificant difference12 RCTs (n = 924)16% vs. 21%0.80 (0.58 to 1.09), I2 = 4.3%
Prostaglandin vs. expectant managementLow-strength evidence of little or no difference4 RCTs (n = 615)27% vs. 26%0.95 (0.68 to 1.33)
Dinoprostone vs. membrane sweepingLow-strength evidence of a small, but nonsignificant difference3 RCTs (n = 339)22% vs. 15%1.44 (0.85 to 2.36)
Silicone vs. latex single-balloon cathetersLow-strength evidence of little or no difference1 RCT (n = 534)39% vs. 40%0.98 (0.80 to 1.22)
Key questionInterventionOutcomeFindingsStudiesIncidenceRelative risk (95% CI)I2 for pooled analyses*
Prostaglandin: outpatient vs. inpatientDinoprostoneInfectionLow-strength evidence of little or no difference2 RCTs (n = 1,120)4% vs. 3%1.39 (0.67 to 3.03)
Mechanical method: outpatient vs. inpatientSingle-balloon catheterBirth traumaLow-strength evidence of little or no difference1 RCT (n = 129)2% vs. 3%0.49 (0.05 to 5.30)
Single-balloon catheterShoulder dystociaLow-strength evidence of a moderate, but non-significant difference1 RCT (n = 129)3% vs. 11%0.28 (0.06 to 1.30)
Outpatient comparison of methodsDinoprostone vs. placeboMeconium aspiration syndromeLow-strength evidence of a small, but nonsignificant difference2 RCTs (n = 134)2% vs. 4%0.76 (0.03 to 22.33)
Prostaglandins vs. placeboShoulder dystociaLow-strength evidence of a small, but nonsignificant difference3 RCTs (n = 270)
2 RCTs (n = 150)
3% vs. 0.70%
6% vs. 1%
Risk difference = 0.01 (−0.02 to 0.04)
3.40 (0.55 to 20.95)
Key questionInterventionOutcomeFindingsStudiesIncidenceRelative risk (95% CI)I2 for pooled analyses*
Mechanical method: outpatient vs. inpatientSingle-balloon catheterUterine infectionLow-strength evidence of little or no difference2 RCTs (n = 259)5% vs. 5%0.99 (0.31 to 3.19)
Outpatient catheter vs. inpatient dinoprostonePostpartum hemorrhageLow-strength evidence of a small, but nonsignificant difference2 RCTs (n = 549)28% vs. 25%1.10 (0.62 to 1.56)
Outpatient comparison of methodsProstaglandins vs. placeboUterine infectionLow-strength evidence of a small, but nonsignificant difference7 RCTs (n = 771)7% vs. 10%0.75 (0.40 to 1.39)
Prostaglandins vs. expected managementUterine infectionLow-strength evidence of little or no difference1 RCT (n = 294)6% vs. 5%1.21 (0.45 to 3.24)
Prostaglandins vs. membrane sweepingUterine infectionLow-strength evidence of a small, but nonsignificant difference2 RCTs (n = 269)7% vs. 4%1.22 (0.56 to 2.75)

Practice Pointers

Cervical ripening is a clinical intervention used to induce labor and increase the likelihood of a vaginal delivery. The likelihood of a successful induction, or cervical favorability, is calculated using the Bishop Score for Vaginal Delivery and Induction of Labor (https://www.mdcalc.com/bishop-score-vaginal-delivery-induction-labor). A score of less than 6 is considered unfavorable and suggests that a ripening agent is needed.2

Cervical ripening can be performed mechanically with a single- or double-balloon catheter, or pharmacologically with oral, intravaginal (insert or gel), or intracervical prostaglandin administration. The choice of method is based on clinician and patient preference.3 Prostaglandins include dinoprostone and misoprostol. Pharmacologic ripening is generally more comfortable for patients than mechanical dilation.

Cervical ripening has historically been performed in the inpatient setting, although more institutions are implementing policies for outpatient ripening, which is the focus of the Agency for Healthcare Research and Quality (AHRQ) review. A potential benefit of cervical ripening in the outpatient setting is decreased time from admission to delivery, which may be more cost-effective.4,5

The AHRQ review included 30 randomized controlled trials and 10 cohort studies of fair quality that included outcomes such as fetal infection, birth trauma, shoulder dystocia, meconium aspiration syndrome, uterine infection, and postpartum hemorrhage. The mean age of participants was 28.8 years, and most were nulliparous at term (mean gestational age = 40 weeks and six days). The most common reason for cervical ripening was postterm pregnancy. Because most studies excluded pregnant people undergoing trial of labor after cesarean delivery, the review is most applicable to uncomplicated singleton pregnancies.

Although cervical ripening in the outpatient setting did not reduce fetal or maternal harms or cesarean rates, the similarity in these outcomes compared with cervical ripening in the inpatient setting suggests that it may be safe to offer outpatient cervical ripening to low-risk patients. Because there were no significant differences in cesarean rates and maternal or fetal harms between pharmacologic and mechanical methods, it is reasonable to choose either in most cases.

The AHRQ review supports current guidance from the American College of Obstetricians and Gynecologists, the Royal College of Obstetricians and Gynaecologists, and other organizations that there is no evidence that any method of cervical ripening is superior to others.2,6 The review's limitations point to areas for future research. Prospective cohort studies with larger sample sizes could potentially identify which ripening method and setting is superior among subgroups, but they would need to control for confounding factors. Because serious maternal and fetal adverse events are relatively uncommon, larger studies may produce stronger recommendations.7

The views expressed in this article are those of the authors and do not reflect the policy or position of the U.S. Army Medical Department, Department of the Army, Department of Defense, or the U.S. government.

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