BACKGROUND AND PURPOSE:

• Vaginal progesterone reduces risk of preterm birth in asymptomatic women with short cervix
• Studies in symptomatic women and short cervix are inconclusive
• Facchinetti et al. (Obstetrics & Gynecology) analyzed the efficacy of progestogens as a tocolytic agent in women with a short cervix

METHODS:

• Randomized Controlled Trial (RCT)
  • Singleton pregnancies between 22 weeks 0 days and 31 weeks and 6 days gestation
  • Arrested preterm labor with a cervix ≤ 25 mm
  • Previous preterm birth excluded
• Participants received one of the following:
  • Vaginal micronized progesterone (200 mg per day)
  • Intramuscular 17[alpha]-hydroxyprogesterone caproate (17-OHPC) (341 mg per week)
  • No treatment (control group)
• Primary Outcome
  • Proportion of women with preterm birth < 37 week of gestation

RESULTS:

• 254 women randomized and 235 women remained for analysis
• Preterm birth rate did not differ significantly between groups:
  • 23% in the 17-OHPC
  • 39% in the vaginal progesterone group
  • 22% in the control group
• Trial stopped during interim analysis (after 50% enrollment) due to futility (nonstatistical increase in preterm birth in vaginal progesterone group and difference even if study continued unlikely to show difference)

CONCLUSION:

• Data in this study contradict previous study by this team
  • Possible explanations include weekly rather than 2x/week
  • More stringent study criteria in this study
    • Exclusion of prior preterm birth and 17-OHPC known to prevent subsequent preterm birth
    • Rigorous and not subjective diagnosis of short cervix
  • Possible that 17-OHPC could still be useful in very high risk (cervix < 15 mm)
• Progestogen use in symptomatic women with a short cervix does not reduce risk for preterm birth once the cervix is ≤ 25 mm

Learn More – Primary Sources:

Progestogens for Maintenance Tocolysis in Women With a Short Cervix: A Randomized Controlled Trial

Related ObG Topics:

17-OHPC Treatment and Prevention of Preterm Birth: Does Timing Matter?

What Is the Quality of Compounded 17-OHPC In US Pharmacies?

SMFM Statement: Choice of Progestogen for Preterm Birth Prevention