Successful pregnancy resulting from cryopreserved pronuclear and cleaved embryos thawed and cultured to blastocysts, refrozen and transferred. A case report

BACKGROUND: Twice-frozen, thawed embryos may have utilization in in vitro fertilization (IVF) cycles. CASE: A 37-year-old woman with endometriosis and infertility returned five years after afresh IVF cycle. Seven cryopreserved embryos (2 pronuclear [pn] and cleaved) were thawed, and five developed to the blastocyst stage. One blastocyst was trans ferred, and the remaining four were recryopreserved. This transfer did not result in pregnancy. The remaining four blastocysts were thawed, and two were transferred resulting in a live, singleton delivery. CONCLUSION: Pregnancy can result from cryopreserved 2-pn and cleaved embryos cultured to blastocysts, refrozen and then transferred at the blastocyst stage.