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

The effectiveness of blastocyst culture and transfer in human in-vitro fert ilization (IVF) was evaluated in a prospective randomized trial in patients having a moderate to good response to gonadotrophin stimulation. Embryos w ere 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 cu lture 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 transfe rred on day 3 (3.7) than on day 5 (2,2). The number of blastocysts transfer red did not affect the implantation rate, and pregnancy rates when either t wo or three blastocysts were transferred were 68 and 87% respectively. The implantation rate of the blastocysts (50.5% fetal heart beat) was significa ntly higher compared to the cleavage stage embryos transferred on day 3 (30 .1%). The percentage of blastocyst development was not affected by the numb er of 2-pronuclear embryos, or by maternal age. Irrespective of the number of blastocysts formed, pregnancy rates mere similar. Furthermore, the pregn ancy rate following blastocyst transfer in patients with 10 or more follicl es at the time of human chorionic gonadotrophin administration was not affe cted by patient age. More than 60% of patients having blastocyst culture an d transfer had supernumerary embryos for cryopreservation, The establishmen t of a pregnancy following thaw and transfer confirmed the viability of cry opreserved blastocysts cultured in the absence of serum or co-culture. The ability to transfer just two blastocysts while maintaining high pregnancy r ates will therefore help to eliminate high order multiple gestations and im prove the overall efficiency of human IVF.