Abstract: Objective To evaluate the impact of sperm midpiece morphology observed under high-power microscope on
embryo development following intracytoplasmic morphologically selected sperm injection. Methods Morphologically normal
sperms from 57 patients undergoing intracytoplasmic sperm injection (ICSI) for male-factor infertility were selected
microscopically (magnification of ×200 or 400) and subjected to motile sperm organellar morphology examination (MSOME) at
high magnification of ×6000. According to the morphology of sperm medpiece, the sperms were divided into 3 groups, namely
group A with a/b of 1-1.2, group B with a/b≥1.5, and group C with irregular morphology. The sperms in the 3 groups were
intracytoplasmically injected in oocytes and the outcomes of the embryos were compared. Results Groups A, B, and C showed
significant differences in the rate of ET-D3 top quality embryo (79.7% vs 55.6 % vs 33.3%) and implantation rate (43.2% vs 11.1%
vs 0% ), but not in the fertilization rate (73.3% vs 80.4% vs 63.5% ), blastocyst formation rate (23.2% vs 22.2% vs 9.09% ),
cryopreservation rate (29.2% vs 25.0 % vs 13.0%), or D3 top quality embryo rate (35.3% vs 37.8% vs 18.8%). Conclusion In ICSI
cycle, selecting morphologically normal sperms for intracytoplasic injection can increase the normal fertilization rate and top
quality embryo rate on the transfer day and improve the implantation rate of the embryo.