Grand Rounds

VICTORIA RCT Results: IM vs Vaginal Progestogen for Preterm Birth

BACKGROUND AND PURPOSE:

Two forms of progestogen therapy, IM 17-OHPC and vaginal micronized natural progesterone, are used for the prevention of preterm birth (PTB)
Choi et al. (BJOG, 2020) compared the efficacy of IM vs vaginal progestogen therapy

Multicenter, randomized, open-label, equivalence trial and a meta-analysis
Participants
- Pregnant women with a history of spontaneous PTB and/or short cervical length (<25 mm)
Interventions
- Vaginal group: 200 mg of vaginal micronized progesterone daily
- IM group: intramuscular injection of 250 mg 17-OHPC weekly
Primary outcome
- PTB before <37 weeks
Results of this study were included in a meta-analysis of other RCTs that compared the 2 interventions

Vaginal group: 119 women | IM group: 128 women
Risks of PTB <37 weeks of gestation did not significantly differ between the two groups (P=0.571)
- Vaginal: 22.7%
- IM: 25.8%
The difference in PTB risk between the two groups was within the equivalence margin of 15%
- 3.1% (95% CI, −7.6 to 13.8%)
Likewise, no differences were seen at <34 weeks or <28 weeks
- <34 weeks: adjusted relative risk (RR): 1.522 (95% CI, 0.741 to 3.126)
- <28 weeks: aRR: 2.088 (95% CI, 0.658 to 6.626)
Meta-analysis (current study plus 5 additional RCTs) showed no significant differences in the risk of PTB between the vaginal and IM progestogen treatments

Vaginal and IM progestogen demonstrated the same efficacy at preventing preterm birth
The authors acknowledge that a significant limitation is combining indications (previous PTB and short cervix)
- Subgroup analysis did not demonstrate differences, however sample size was too small to draw a definitive conclusion

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