Blastomere number and pregnancy rates in the succeeding in vitro fertilization cycle in women who formed all embryos with < or = 5 blastomeres.

PURPOSE: To determine the likelihood of pregnancy following the transfer of embryos all with slow cleavage to day 3. Furthermore to determine the likelihood that if slow cleavage happens once, it is likely to repeat. METHODS: A 10-year retrospective review of in vitro fertilization-embryo transfer (IVF-ET) cycles was performed to identify day 3 embryo transfers where none of the embryos had > 5 blastomeres. The pregnancy rate was then determined. If pregnancy did not occur and another IVF-ET cycle was performed it was determined what percentage of those cycles also showed 100% slow cleavage. RESULTS: The ongoing delivered pregnancy rate was 22.3% and the implantation rate was 15.6%. Of the 90 women trying another cycle 82.2% had at least one embryo with six blastomeres. The implantation rate for cycle number 2 for those with at least one 6-cell embryo was 18% (34/187) but was zero (0/17) for those not having at least a 6-cell embryo in cycle number 7. CONCLUSIONS: These data can help a couple decide whether to pursue a second cycle following an IVF-ET cycle with 100% slow cleavage embryos.