Fertilization rates of small-head sperm in conventional IVF and ICSI

Five men produced 23 ejaculates in 23 assisted reproductive technology cycles for semen analysis. In 11 of the 14 ICSI cycles and in 5 of the 9 IVF cycles, small-head sperm were found in more than 70% of the cells, having a length of < 3.5 micro m and a width of < 2 micro m. In 6 of the 14 ICSI cycles, the embryologist who performed the ICSI was not alerted to e presence of small-head sperm. Subsequent fertilization rate was significantly lower than a) the fertilization rate of the remaining 5 ICSI cycles that acted as a control, in which the embryologist was alerted to the presence of small-head sperm, and b) was lower than the 3 ICSI cycles with normal sperm head (p < .05). The 8 cell embryo and blastocyst rates in the former group were also decreased, although not significantly, compared to the latter groups. Likewise, in the 5 IVF cycles with small-head sperm, the fertilization rate was significantly lower than in the 4 IVF with normal sperm head (p < .05). Embryologists should be alerted when a high percentage of small-head sperm are detected during routine semen analysis because they may be associated with reduced fertilization and embryo outcome.