Vaginal progesterone supplementation is routine treatment after IVF with fresh embryo transfer, but it is uncertain whether vaginal progesterone after frozen embryo transfer in natural cycles is efficacious in terms of increasing the chance of a live birth.~The ProFET study is a multicenter, open randomized, controlled trial planning to include 1800 women, intended to undergo a FET in a natural cycle.~Primary objectives are to investigate if luteal phase support by vaginal progesterone, is superior to no luteal phase support, in terms of live birth rate per woman after a frozen embryo transfer, in a natural cycle and if 7 weeks of treatment is superior to 3 weeks duration.~Secondary objectives are to compare groups regarding pregnancy outcomes including biochemical pregnancy, clinical, ongoing and term pregnancy rates, as well as rates of miscarriage, termination of pregnancy, and ectopic pregnancy.~Secondary objectives are also perinatal and obstetrics outcomes, self-reported side effects, adverse events and cost effectiveness.~The investigators will also analyze the effect of S-Progesterone level before FET on the chance of achieving live birth and secondary pregnancy outcomes.
The ProFET study aims to investigate if luteal phase support by vaginal progesterone, is superior to no luteal phase support, in terms of live birth rate per woman after a frozen embryo transfer (FET), in a natural cycle (NC) after in-vitro fertilization (IVF), and if 7 weeks of treatment is superior to 3 weeks duration.