Luteal Phase Progesterone Support Does Not Improve Ongoing Pregnancies In True Natural Cycle Cryopreserved Blastocyst Embryo Transfers.

Background: More than 67% of all embryos transferred in the United States involve frozen-thawed embryos. Progesterone supplementation is necessary in medicated cycles in order to luteinize the endometrium and prepare it for implantation, but little data is available if this is necessary in true natural cycles. We evaluated the use of progesterone luteal phase supplementation for cryopreserved/warmed blastocyst transfers in natural cycles not using an ovulatory trigger.Methods: Retrospective cohort study in a single academic medical center. We studied the use of progesterone supplementation beginning in the luteal phase and continued until 10 weeks gestational age in patients undergoing true natural cycle cryopreserved blastocyst transfer. Our outcome measures were ongoing pregnancy rate, positive serum beta human chorionic gonadotropin (HCG) level, implantation rate, clinical pregnancy rate, miscarriage/abortion rate, ectopic pregnancy rate, and multifetal gestation rate. Categorical data were analyzed utilizing Fisher’s exact test and non-parametric data were analyzed using the Wilcoxon rank sum test. We a priori adjusted for age.Results: 229 patients were included in the analysis with 149 receiving luteal phase progesterone supplementation and 80 receiving no luteal phase support. Patient demographic and cycle characteristics, and embryo quality were similar between the two groups. No difference was seen in ongoing pregnancy rate (49.0% vs. 47.5%, p=0.8738), clinical pregnancy rate (50.3% vs. 47.5%, p= 0.7483), positive HCG rate (62.4% vs. 57.5%, p=0.5965), miscarriage/abortion rate (5.4% vs. 2.5%, p=0.2622), ectopic pregnancy rate (0% vs. 1.3%, p=0.3493), or multifetal gestations (7.4% vs. 3.8%, p=0.3166).Conclusion(s): The addition of progesterone luteal phase support in true natural cycle cryopreserved blastocyst transfers does not improve cycle outcomes. Capsule: Progesterone supplementation as luteal phase support in true natural cycle cryopreserved blastocyst transfers does not improve ongoing pregnancies.