OBJECTIVETo compare the criteria of sperm morphology evaluation in the fifth edition of WHO Laboratory Manual for the Examination and Processing of Human Semen and those in the fourth edition, and to know the changes in the criteria of sperm morphology evaluation in the new edition.

METHODSNine technicians from Zhejiang Human Sperm Bank evaluated the morphology of 1 000 spermatozoa in 96 sperm morphological pictures according to the criteria in the fourth and fifth editions of WHO Laboratory Manual, respectively.

RESULTSThe percentage of morphologically normal sperm by the criteria of the fifth edition was (26.50 +/- 5.06)%, significantly higher than (11.39 +/- 3.17)% by the fourth edition (P < 0.05), while the rates of sperm head and tail defects based on the former were (64.26 +/- 7.66)% and (10.92 +/- 2.03)%, significantly lower than (76.11 +/- 8.18)% and (39.89 +/- 3.85)% according to the latter (P < 0.05). There were no significant differences in the rates of sperm midpiece defects and excessive residual cytoplasm by the fifth and fourth editions ([16.46 +/- 3.08]% vs [15.22 +/- 3.51 ]% and [4.24 +/- 1.66]% vs [3.87 +/- 1.68]%, P > 0.05).

CONCLUSIONThe criteria of sperm morphology evaluation in the fifth edition of WHO Laboratory Manual are less strict than those in the fourth, and the percentage of morphologically normal sperm is higher according to the fifth edition.