Objective: To compare the efficacy of two types of progestogen therapy for preventing preterm birth (PTB) and to review the relevant literature.
Design: A multicentre, randomised, open-label, equivalence trial and a meta-analysis.
Setting: Tertiary referral hospitals in South Korea.
Population: Pregnant women with a history of spontaneous PTB or short cervical length (<25 mm).
Methods: Eligible women were screened and randomised at 16-22 weeks of gestation to receive either 200 mg of vaginal micronised progesterone daily (vaginal group) or an intramuscular injection of 250 mg 17α-hydroxyprogesterone caproate weekly (IM group). Stratified randomisation was carried out according to participating centres and indications for progestogen therapy. This trial was registered at ClinicalTrials.gov (NCT02304237).
Main outcome measure: Preterm birth (PTB) before 37 weeks of gestation.
Results: A total of 266 women were randomly assigned and a total of 247 women (119 and 128 women in the vaginal and IM groups, respectively) were available for the intention-to-treat analysis. Risks of PTB before 37 weeks of gestation did not significantly differ between the two groups (22.7 versus 25.8%, P = 0.571). The difference in PTB risk between the two groups was 3.1% (95% CI -7.6 to 13.8%), which was within the equivalence margin of 15%. The meta-analysis results showed no significant differences in the risk of PTB between the vaginal and IM progestogen treatments.
Conclusion: Compared with vaginal progesterone, treatment with intramuscular progestin might increase the risk of PTB before 37 weeks of gestation by as much as 13.8%, or reduce the risk by as much as 7.6%, in women with a history of spontaneous PTB or with short cervical length.
Tweetable abstract: Vaginal and intramuscular progestogen showed equivalent efficacy for preventing preterm birth before 37 weeks of gestation.
Keywords: Preterm birth; prevention; progestogen; short cervical length.
© 2020 Royal College of Obstetricians and Gynaecologists.