To determine whether vaginal progesterone for programmed endometrial preparation is noninferior to intramuscular progesterone in terms of live birth rates from frozen embryo transfer (FET).
Three-armed, randomized, controlled noninferiority trial.
Multicenter fertility clinic.
A total of 1,346 volunteer subjects planning vitrified-warmed transfer of high-quality nonbiopsied blastocysts were screened, of whom 1,125 subjects were ultimately enrolled and randomly assigned to treatment.
The subjects were randomly assigned to receive, in preparation for FET, 50 mg daily of intramuscular progesterone (control group), 200 mg twice daily of vaginal micronized progesterone plus 50 mg of intramuscular progesterone every third day (combination treatment), or 200 mg twice daily of vaginal micronized progesterone.
Main Outcome Measure(s)
The primary outcome was live birth rate per vitrified-warmed embryo transfer. The secondary outcomes were a positive serum human chorionic gonadotropin test 2 weeks after FET, biochemical pregnancy loss, clinical pregnancy, clinical pregnancy loss, total pregnancy loss, serum luteal progesterone concentration 2 weeks after FET, and patient’s experience and attitudes regarding the route of progesterone administration, on the basis of a survey administered to the subjects between FET and pregnancy test.
A total of 1,060 FETs were completed. The live birth rate was significantly lower in women receiving only vaginal progesterone (27%) than in women receiving intramuscular progesterone (44%) or combination treatment (46%). Fifty percent of pregnancies in women receiving only vaginal progesterone ended in miscarriage.
The live birth rate after vaginal-only progesterone replacement was significantly reduced, due primarily to an increased rate of miscarriage. Vaginal progesterone supplemented with intramuscular progesterone every third day was noninferior to daily intramuscular progesterone, offering an effective alternative regimen with fewer injections.
Clinical Trial Registration Number