Teratozoospermia influences fertilization rate in vitro but not embryo quality

The purpose of this study was to retrospectively compare the overall results and embryo quality in 102 cycles of in-vitro fertilization (IVF)-embryo transfer using normal frozen donor semen (group D) and 94 cycles of IVF-embryo transfer using husbands' teratozoospermic sperm (group T). Donor semen was purchased from men with proven fertility and normal semen parameters. Teratozoospermia was defined in group T as the presence of <20% of normal spermatozoa in semen on the day of oocyte retrieval. Exclusion criteria were a sperm count <10 x 10(6)/ml or with <10% progressive motility. Fertilization rate, transfer rate and number of transferred embryos per cycle were significantly lower in the teratozoospermic group (45 vs 72%, 66 vs 96%, 1.7 vs 2.9%, respectively). Pregnancy rate per cycle was also lower, but not significantly (18 vs 28%). However, pregnancy rate per transfer, implantation rate per transferred embryo and take home baby rate were comparable (27 vs 30%, 15 vs 15%, 21 vs 24%, respectively). Similarly, embryo quality in terms of number of embryos displaying fragmentations or irregular cells, cleavage stages and embryo scores were comparable. When group T was divided into two subgroups according to sperm count (group T1: sperm count = 10-20 x 10(6)/ml; group T2: sperm count >20 x 10(6)/ml), there was no difference between them with regard to fertilization rate, pregnancy rate or embryo quality. This study confirms low pregnancy rate per cycle in IVF-embryo transfer using teratozoospermic semen, but demonstrates for the first time that embryo quality and viability are not impaired. It is proposed that the poor pregnancy rate per cycle obtained is due only to the poor fertilization rate, and to the subsequent limited choice of embryos to be transferred.