Dizygotic twin delivery following in vitro fertilization and transfer of thawed blastocysts cryopreserved at day 6 and 7.

OBJECTIVE: To report the first conception and delivery following transfer of thawed human blastocysts maintained in extended in vitro culture with cryopreservation at day 6 and 7.
DESIGN: Case report.
SETTING: Major urban infertility referral center. PATIENT(S): A 26-year-old woman with pelvic endometriosis and two prior unsuccessful in vitro fertilization/embryo transfer (IVF-ET) attempts. INTERVENTION(S): The patient underwent controlled ovarian hyperstimulation using a combined FSH + hMG protocol, and 24 oocytes were retrieved. MAIN OUTCOME MEASURE(S): Dizygotic twin delivery after IVF and intracytoplasmic sperm injection (ICSI), assisted embryo hatching, and ultrasound-guided transfer of cryopreserved blastocysts. RESULT(S): After three embryos were subjected to assisted hatching, they were transferred fresh on day 3, but no implantation occurred. All nontransferred embryos (n = 11) were observed during extended in vitro culture and three blastocysts were selected for cryopreservation on day 6 and 7; thaw and transfer occurred the following month and a pregnancy was achieved. Dizygotic twins (female/female) were delivered by cesarean in the early third trimester. CONCLUSION(S): Substantial advancements have been made in the field of embryo cryogenics and in vitro fertilization, but controversy remains regarding the value of freezing late-developing human blastocysts. Here we describe the first reported live births with IVF after extended in vitro culture and cryopreservation at day 6 and 7 after fertilization.