OBJECTIVETo evaluate the accuracy of a scoring system combining zygote and embryo morphology in predicting the outcome of in vitro fertilization (IVF) treatment.

METHODSIn a study group, 117 consecutive IVF or intracytoplasmic sperm injection (ICSI) cycles with embryo transfer were carried out and 312 embryos were scored using a combined scoring system (CSS) of zygote and embryo morphology before transplantation. In a control group, a total of 420 IVF or ICSI cycles were carried out and 1176 embryos were scored using a cumulative embryo score (CES). The effects of the combined scoring system on the embryo implantation rate and pregnancy rate per cycle were analyzed.

RESULTSUsing the combined scoring system, the embryo implantation rate (27.6%) and the clinical pregnancy rate (48.7%) were significantly higher than those in the control group (20.8% and 38.6%, respectively). Also, the implantation rate of embryos scoring>or=70 (38.5%: 82 sacs/213 embryos) was significantly higher (P<0.001) than that of embryos scoring<70 (4%: 4 sacs/99 embryos). The pregnancy rate of patients with embryos scoring>or=70 using the combined scoring system (66.7%) was significantly higher (P<0.001) than that of patients with embryos scoring>or=20 using the cumulative embryo score (59.0%).

CONCLUSIONThe results suggest that selecting embryos with a high score (>or=70) using the combined scoring system could increase the implantation rate and pregnancy rate, and that using a scoring system combining assessments of human zygotes and pre-implantation embryos might predict IVF outcomes more accurately than using a cumulative embryo score.