BACKGROUND AND PURPOSE:

• de Vaan et al. (Cochrane Reviews, 2019) compared mechanical to pharmacological methods for labor induction (third trimester)

METHODS:

• Systematic review and meta-analysis update
• Data sources
  • Cochrane Pregnancy and Childbirth’s Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP), and reference lists of retrieved studies in 2018
• Inclusion criteria
  • Clinical trials that compared mechanical vs cervical ripening methods for labor induction in the third trimester
• Data synthesis and analysis
  • Two independent authors provided study reviews
  • GRADE criteria were followed
• Mechanical methods included
  • balloon catheter
  • Laminaria or synthetic equivalent
  • Catheter to inject fluid into the extra-amniotic space (EASI)
• Comparisons
  • Specific mechanical methods vs with prostaglandins or with oxytocin
  • Single balloon compared to a double balloon
  • Addition of prostaglandins or oxytocin to mechanical methods compared with prostaglandins or oxytocin alone

RESULTS:

• Total of 113 trials | 22,373 women | 21 comparisons | All studies were RCTs
• Quality of evidence
  • Overall evidence was of very-low to moderate quality
  • All evidence was downgraded due to lack of blinding and imprecise effect estimates

Balloon vs Vaginal PGE2

• Little or no difference in vaginal deliveries not achieved within 24 hours (low-quality evidence)
  • Average risk ratio (RR) 1.01 (95% CI, 0.82 to 1.26)
• Probably little or no difference in caesarean delivery not achieved within 24 hours (moderate-quality evidence)
  • RR 1.00 (95% CI, 0.92 to 1.09)
• Balloon catheter probably reduces the risk of
  • Uterine hyperstimulation with FHR changes
    • RR 0.35 (95% CI, 0.18 to 0.67)
  • Serious neonatal morbidity or perinatal death
    • RR 0.48 (95% CI, 0.25 to 0.93)
• Balloon catheter may slightly reduce the risk of NICU admission
  • RR 0.82 (95% CI, 0.65 to 1.04)
• Uncertain whether there is a difference in
  • Serious maternal morbidity or death
  • Five-minute Apgar score < 7

Balloon vs Low-dose Vaginal Misoprostol

• Uncertain whether there is a difference in vaginal deliveries not achieved within 24 hours
  • RR 1.09 (95% CI, 0.85 to 1.39)
• A balloon catheter probably reduces the risk of uterine hyperstimulation with FHR changes
  • RR 0.39 (95% CI 0.18 to 0.85)
• Balloon catheter may increase the risk of a caesarean section
  • RR 1.28 (95% CI, 1.02 to 1.60)
• Uncertain whether there is a difference in
  • Serious neonatal morbidity or perinatal death
  • Serious maternal morbidity or death
  • Five-minute Apgar score < 7
  • NICU admissions

Balloon versus Low-dose Oral Misoprostol

• Balloon catheter probably increases the risk of a vaginal delivery not achieved within 24 hours
  • RR 1.28 (95% CI, 1.13 to 1.46)
• Balloon catheter probably slightly increases the risk of a cesarean section
  • RR 1.17 (95% CI, 1.04 to 1.32)
• It is uncertain whether there is a difference in
  • Uterine hyperstimulation with FHR changes
  • Serious neonatal morbidity or perinatal death
  • Serious maternal morbidity or death
  • Five-minute Apgar scores < 7
  • NICU admissions

Additional Comparisons

• No difference between single and double balloon devices
• Laminaria comparisons resulted in uncertain results, expect for comparison vs vaginal prostaglandin E2, which probably reduces risk of uterine hyperstimulation with FHR changes
• Mechanical method and low dose misoprostol versus misoprostol alone
  • Uncertain results for primary outcomes, including probabilities for vaginal delivery, uterine hyperstimulation, cesarean section, serious maternal and perinatal morbidity and mortality
    • Combining mechanical method and misoprostol probably reduces risk of unfavorable cervix at 24 hours and meconium stained fluid

CONCLUSION:

• Mechanical induction with balloon catheter is probably as effective as vaginal PGE2 (low to moderate-quality evidence)
  • Balloon catheter seems to be the safer method of induction
  • The authors conclude that more research is probably not warranted
• Balloon catheter may be slightly less effective than oral misoprostol (moderate-quality evidence)
  • Safety comparison between the two methods remains unclear
• Balloon catheter may be less effective that vaginal misoprostol (Low-quality evidence)
  • Balloon catheter is probably the safer of the two methods
• The authors conclude

The advantages of mechanical methods are their wide availability and the low cost of the devices, especially Foley catheters. Storage and preservation of mechanical devices is less problematic than PGE2, which should be kept refrigerated. However, special attention should be paid to contraindications (e.g. low‐lying placenta) when inserting these devices.

Learn More – Primary Sources:

Mechanical methods for induction of labour

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