Maintenance Treatment With Vaginal Progesterone or Placebo Delayed Preterm Birth More Efficiently Than Intravenous Tocolysis Alone – A Randomized Controlled Trial

Abstract Objective To evaulate the efficacy of maintenance treatment with vaginal progesterone gel compared to placebo in women after the onset of preterm labor.Material and Methods A randomized controlled trial at a university hospital in Sweden in 2009 − 18. Healthy women with singleton pregnancy and early preterm labor were randomized to daily progesterone gel 90 mg (n = 29) or placebo (n = 29) after standard intravenous tocolysis. Women with intravenous tocolysis alone (n = 29) served as a reference group. Results The latency to delivery was 58 ± 34 days with progesterone, 64 ± 51 days with placebo and 2 ± 2 days in the reference group (p < 0.0001 respectively). The rate of preterm birth < 34 weeks was 34% after progesterone, 38% after placebo and 100% in the reference group (progesterone vs reference p = 0.01 and placebo vs reference p = 0.02). The composite neonatal morbidity and length of neonatal intensive care were lower after progesterone and placebo compared to the reference group (p < 0.0001 respectively).Conclusion Maintenance treatment with vaginal progesterone gel or placebo delayed preterm birth more efficiently than intravenous tocolysis alone, suggesting an effect of the placebo gel rather than of progesterone. We conclude, that the placebo gel reinforced the physiological barrier at the uterine cervix which protects the pregnancy from pathogen invasion and uterine infection leading to preterm birth.