Hormonal Induction of Endometrial Receptivity for Fresh or Frozen Embryo Transfer
Hormonal Induction of Endometrial Receptivity for Fresh or Frozen Embryo Transfer Part I & II: An Overview by Richard J. Paulson, MD
Date: February 19, 2025
Author: ASRM
Dive into the history, current practices, and ongoing debates surrounding progesterone administration in assisted reproductive technology (ART) with Dr. Richard Paulson, a seasoned expert in IVF and reproductive medicine from the University of Southern California.
In a two-part ASRMed Talk, Dr. Paulson traces the origins of hormonal induction back to the beginning, with the start of egg donation. The world's first pregnancy in an agonadal recipient took place in 1983. The patient took 50 milligrams twice a day of both oral estrogen and vaginal progesterone, and one two-cell embryo was transferred on the second day of progesterone, meaning the progesterone started when that embryo was at the pre-nuclear stage. After this first procedure, the preparation of the endometrium was extended to surrogacy, and, as embryo cryopreservation became more efficient, it was used for preparation of the endometrium prior to frozen embryo transfer. Today, this use is the most common.
He also delves into current practices for preparing the endometrium using hormonal induction, stating that “estrogen and progesterone are all that have ever been shown to be necessary and nothing added to it has actually been shown to make a difference.” There are two common estrogen induction methods: oral and transdermal. Progesterone is present at much higher levels in the body, requiring higher doses and making intramuscular and vaginal methods the only viable options.
In Part II, he addresses the ongoing debate regarding vaginal versus intramuscular progesterone, recounting his own research that revealed that vaginal administration yielded higher endometrial tissue levels despite lower serum levels. He acknowledges recent studies that challenged the equivalence of these methods, but maintains his belief that vaginal progesterone is equally effective.
Furthermore, Dr. Paulson addresses the crucial aspect of progesterone timing, advocating for administration on the evening of the day of ovulation or the following morning. He also discusses the limitations of endometrial receptivity tests like the ERA, emphasizing the lack of proven clinical superiority. In conclusion, Dr. Paulson underscores the simplicity of endometrial preparation, reaffirming that the established protocols remain effective. He expresses optimism for the future, particularly the potential for subcutaneous progesterone administration, and reiterates the enduring importance of estrogen and progesterone in achieving successful outcomes in ART.
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