Addition of intramuscular progesterone to vaginal progesterone in hormone replacement therapy in vitrified-warmed blastocyst transfer cycles.

Research Question: Does intramuscular progesterone supplementation ensure ongoing pregnancy rates (OPR) comparable with vaginal progesterone only in hormone replacement therapy cycles for vitrified-warmed embryo transfer; and is there a window of serum progesterone concentration out of which reproductive outcomes may be negatively affected?
Design: Retrospective longitudinal cohort study carried out at a single IVF clinic. In total, 475 consecutive, day-5 to day-6 vitrified-warmed embryo transfer cycles using hormone replacement therapy regimen were included. Vaginal progesterone only was given to 143 patients; supplementation of vaginal progesterone only with intramuscular progesterone supplementation every third day was given to 332 patients. On the sixth day of progesterone administration, immediately before frozen-thawed embryo transfer, circulating progesterone levels were measured. Main outcome measure was OPR.
Results: The baseline demographic features and embryological data of the vaginal progesterone only and intramuscular progesterone supplementation groups were comparable. The OPR were 48.3% and 51.8%, respectively (P = 0.477). Neither the circulating progesterone level nor the type of progesterone administration were independent predictors of OPR. The effect of serum progesterone levels on OPR was evaluated by percentiles (<10%, 10-49%, 50-90% and >90%), taking 50-90% as the reference sub-group. All percentiles in the intramuscular progesterone supplementation group and in the vaginal progesterone only group had similar OPR.
Conclusions: Intramuscular progesterone supplementation every third day, overall, does not enhance OPR compared with vaginal progesterone only.
(Copyright © 2020 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.)