Characterization of a top quality embryo, a step towards single-embryo transfer

In most in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICST ) programmes approximately one ongoing pregnancy in three is multiple, The need to characterize embryos with optimal implantation potential is obvious . We retrospectively examined all of 23 double transfers resulting in ongoi ng twins, occurring between January 1, 1996 and May 19, 1997, Characteristi cs of these top quality embryos were absence of multinucleated blastomeres, four or five blastomeres on day 2, seven or more cells on day 3, and less than or equal to 20% anucleated fragments. In a subsequent series of 400 IV F/ICSI cycles (out of which 372 were selected for embryo transfer) from May 20, 1997 to July 31, 1998, only women <38 years of age had multiple pregna ncies: after 221 transfers of two embryos, 45/116 (39%) were multiple, and after 77 transfers of >2 embryos, 11/31 (35%) were multiple, We applied our top quality criteria to the 221 double transfers: 106 transfers with two t op embryos resulted in 65 (63%) ongoing pregnancies with 37 (57%) twins, 65 transfers with one top embryo in 38 (58%) ongoing pregnancies with eight ( 21%) twins. Tn the group without top embryos, 12/52 (23%) ongoing singleton s occurred, with no twins. The corresponding ongoing implantation rates wer e 49, 35 and 12%, This analysis suggests that single embryo transfer with a n acceptable pregnancy rate might be considered if a top quality embryo is available.