Grand Rounds

Do Progestogens Prevent Preterm Birth in Symptomatic Pregnancies with a Short Cervix?

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

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

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)

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

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