Embryo Cryopreservation Strategy May Improve Live Birth for Women Underwent In Vitro Maturation After Early Oocyte Retrieval: A Retrospective Cohort Study.

There is limited clinical research investigating the optimal transplantation strategy in early oocyte retrieval cycles. We aimed to assess whether the maturation of oocytes from early oocyte retrieval influenced pregnancy outcomes, and to find the optimal embryo transfer strategy (fresh or frozen-thawed embryo transfers) for patients who had early oocyte retrieval and underwent in vitro maturation (IVM). A retrospective cohort study was conducted in a university-based reproductive medical center. A total of 234 women who underwent single embryo transfer after early oocyte retrieval were included. The primary outcome was live birth rate. The live birth rate (12.5% vs. 27.5%, p = 0.005, adjusted p = 0.010) was significantly lower in IVM cycles compared with no IVM cycles. There was a significant decrease in live birth (3.6% vs. 19.0%, p = 0.008, adjusted p = 0.011) and a markedly elevated early pregnancy loss rate (62.5% vs. 11.1%, p = 0.014, adjusted p = 0.012) for IVM fresh cycles compared with no IVM fresh cycles. However, these findings were not repeated in subgroup analysis when frozen-thaw embryos were transferred. These results indicate that patients who underwent early oocyte retrieval and then IVM-intracytoplasmic sperm injection should be recommended the embryo cryopreservation strategy. Resynchronization of the embryo and the endometrium in frozen-thaw embryo transfer cycles may optimize live birth and decrease early pregnancy loss in IVM-intracytoplasmic sperm injection cycles after early oocyte retrieval.