Maintenance treatment with progesterone gel and the gel base delayed preterm birth more effectively than intravenous tocolysis alone – a randomized controlled trial

Introduction The aim was to evaluate the effect of maintenance treatment with progesterone gel compared to the gel base in delaying preterm birth among women with spontaneous preterm labor. Materials and Methods A randomized controlled trial in Sweden in 2009 − 18. Women with spontaneous preterm labor were randomized to daily progesterone gel 90 mg (n = 29) or gel base doses (n = 29) after intravenous tocolysis. Results The latency to delivery was 58 ± 34 days with progesterone gel and 64 ± 51 days with gel base (p = 0.83), compared to 2 days after intravenous tocolysis alone (both p < 0.001). The rate of preterm birth before 34 weeks was 34 % after progesterone gel and 38 % after gel base (p = 0.34). The composite neonatal morbidity (p = 0.65) and neonatal intensive care unit admission (p = 0.12) did not differ between the groups. Conclusion Preterm birth was delayed more effectively after both progesterone and gel base compared to intravenous tocoylsis alone, suggesting an effect of the gel base. We conclude, that the acidic gel base reinforced the physiological barrier at the uterine cervix, which counteracted ascending pathogen invasion and thereby delayed preterm birth.