Vaginal micronized progesterone and risk of preterm delivery in high-risk twin pregnancies: secondary analysis of a placebo-controlled randomized trial and meta-analysis

Objectives: Progesterone treatment reduces the risk of preterm delivery in high-risk singleton pregnancies. Our aim was to evaluate the preventive effect of vaginal progesterone in high-risk twins.

Methods: This was a subanalysis of a Danish-Austrian, double-blind, placebo-controlled, randomized trial (PREDICT study), in which women with twin pregnancies were randomized to daily treatment with progesterone or placebo pessaries from 20-24 weeks until 34 weeks' gestation. This subpopulation consisted of high-risk pregnancies, defined by the finding of cervical length ≤ 10th centile at 20-24 weeks' gestation or history of either spontaneous delivery before 34 weeks or miscarriage after 12 weeks. Primary outcome was delivery before 34 weeks. Secondary outcomes were complications for infants including long-term follow-up by Ages and Stages Questionnaire (ASQ) at 6 and 18 months of age.

Results: In 72 (10.6%) of the 677 women participating in the PREDICT study, the pregnancy was considered to be high-risk, including 47 with cervical length ≤ 10th centile, 28 with a history of preterm delivery or late miscarriage and three fulfilling both criteria. Baseline characteristics for progesterone and placebo groups were similar. Mean gestational age at delivery did not differ significantly between the two groups either in patients with a short cervix (34.3 ± 4.1 vs. 34.5 ± 3.0 weeks, P = 0.87) or in those with a history of preterm delivery or late miscarriage (34.6 ± 4.2 vs. 35.2 ± 2.7 weeks, P = 0.62). Similarly, there were no significant differences between the treatment groups in maternal or neonatal complications and mean ASQ score at 6 and 18 months of age.

Conclusion: In high-risk twin pregnancies, progesterone treatment does not significantly improve outcome.