A prospective randomized trial of blastocyst culture and transfer in in- vitro fertilization

Abstract

The effectiveness of blastocyst culture and transfer in human in-vitro fertilization (IVF) was evaluated in a prospective randomized trial in patients having a moderate to good response to gonadotrophin stimulation. Embryos were transferred either on day 3 after culture to around the 8-cell stage in Ham's F-10 medium supplemented with fetal cord serum, or on day 5 after culture to the blastocyst stage in the sequential serum-free media G 1.2 and G 2.2. The pregnancy rates after transfer on day 3 or day 5 were equivalent, 66 and 71% respectively; however, significantly more embryos were transferred on day 3 (3.7) than on day 5 (2.2). The number of blastocysts transferred did not affect the implantation rate, and pregnancy rates when either two or three blastocysts were transferred were 68 and 87% respectively. The implantation rate of the blastocysts (50.5% fetal heart beat) was significantly higher compared to the cleavage stage embryos transferred on day 3 (30.1%). The percentage of blastocyst development was not affected by the number of 2-pronuclear embryos, or by maternal age. Irrespective of the number of blastocysts formed, pregnancy rates were similar. Furthermore, the pregnancy rate following blastocyst transfer in patients with 10 or more follicles at the time of human chorionic gonadotrophin administration was not affected by patient age. More than 60% of patients having blastocyst culture and transfer had supernumerary embryos for cryopreservation. The establishment of a pregnancy following thaw and transfer confirmed the viability of cryopreserved blastocysts cultured in the absence of serum or co-culture. The ability to transfer just two blastocysts while maintaining high pregnancy rates will therefore help to eliminate high order multiple gestations and improve the overall efficiency of human IVF.

Selection of Embryos for Day-3 Transfer at the Pronuclear-Stage and Pronuclear-Stage Cryopreservation Results in High Delivery Rates in Fresh and Frozen Cycles

“…The introduction in 1998 of blastocyst culture caused us to reevaluate our embryo culture and cryopreservation strategy. The initial studies on blastocyst transfer showed that the two possible advantages of blastocyst culture were an improved rate of pregnancy in the fresh cycle and a decrease in high-order multiple pregnancies (14)(15)(16). We sought to determine whether additional strategies could enhance our long-standing approach of cryopreserving extra embryos at the PN-S. We were interested in determining whether this enhanced approach might be an effective alternative to the more commonly used strategy of leaving all embryos in culture for selection of the best embryos at the cleavage or blastocyst stages.…”

“…These were higher than those reported in most blastocyst studies even though only 0.88, 0.80, and 0.61 more embryos were cultured for Groups I, II, and III, respectively, than the number transferred. Pregnancy and implantation rates with blastocyst transfer have ranged from 21 to 77% and 9-62%, respectively (2,5,6,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). With blastocyst transfer, all embryos are retained in culture to ensure at least two high-quality blastocysts are available for transfer.…”

“…With current culture techniques, only 30-50% of zygotes typically develop into normal blastocysts which results in fewer patients having cryopreserved embryos and fewer numbers of embryos frozen per cycle (2,(5)(6)(7)15,17,18,(20)(21)(22)25,27,29).…”

“…During the past decade, increasing emphasis has been placed on limiting IVF-ET multiple pregnancies (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)29,(31)(32)(33)(34). Culture of embryos to the blastocyst stage has been advocated as a method for reducing multiple births while maintaining high fresh cycle pregnancy rates (15,16).…”

“…Culture of embryos to the blastocyst stage has been advocated as a method for reducing multiple births while maintaining high fresh cycle pregnancy rates (15,16). To date, blastocyst transfers have reduced high-order multiple pregnancies, that is triplet or greater, but not overall multiple rates (16,21,31).…”