Use of co-culture of human embryos on Vero cells to improve clinical implantation rate.

Co-culture of human embryos (n = 384 cycles) to the blastocyst stage using Vero cell monolayers was carried out between August 1995 and December 1997. A total of 2868 zygotes were co-cultured and 1027 embryos reached the blastocyst stage (blastocyst formation rate 35.8%). The blastocysts were frozen in 43.7% of patients. A mean of 1.8 blastocysts was transferred per patient and 95 pregnancies were obtained (pregnancy rate/cycle 24.7%). The blastocyst implantation rate was 23.6%. Miscarriage occurred in 15 patients (15.7%) and ectopic pregnancy in three (3.1%) patients. The multiple pregnancy rate was 32.6%. No differences were observed in the blastocyst rate between poor, normal or high response patients. Blastocyst formation was significantly lower when frozen donor spermatozoa were used. Significantly higher pregnancy rates per transfer and blastocyst implantation rates were attained when embryos were transferred on days 5 or 6 compared with day 7. No advantage was observed when co-culture was used in first cycle IVF patients, in comparison with conventional day 2 replacements. The use of blastocysts for preimplantation genetic diagnosis (PGD) increases the diagnostic reliability and widens diagnostic possibilities. A total of 215 cycles with frozen-thawed co-cultured blastocysts were carried out, with a pregnancy rate of 22.7% per replacement.