A randomized controlled study of luteal support therapy (using intramuscular injections of progesterone and/or human chorionic gonadotropin) was conducted in a trial designed to minimize variables that might adversely affect the chance of pregnancy. After applying rigid selection criteria, 207 women were recruited into one of four groups. Mathematical modeling was applied to the results to determine if there were degrees of improvement in uterine receptivity relative to various grades of embryo quality ('E' factor). Although the trial size was insufficient to enable the detection of significant improvements in the pregnancy rates that ranged from 27.5% for non-treatment to 41.2% for those receiving combined treatment, the birth rates were significantly better with luteal support (11.8% versus 29.4%). Similarly, the overall implantation rate just failed to reach statistical significance for luteal support, but the ongoing implantations were significantly better (3.6% versus 9.0%). Data modeling indicated that luteal support, particularly with the combined regimen, could improve the ongoing implantation rate by up to 2.5-fold when the E factor was poorest.
Yovich, J. L., Edirisinghe, W. R., & Cummins, J. M. (1991). Evaluation of luteal support therapy in a randomized controlled study within a gamete intrafallopian transfer program. Fertility and Sterility, 55(1), 131–139. https://doi.org/10.1016/S0015-0282(16)54072-2