Evaluation of a cut-off value for normal sperm morphology using strict criteria to predict fertilization after conventional in-vitro fertilization and embryo transfer in asthenozoospermia.

Abstract

The predictive value of sperm morphology evaluation using strict criteria (MEUSC) on fertilization and pregnancy rates was evaluated in 60 couples undergoing in-vitro fertilization (IVF) and embryo transfer. In all, 47 of the male partners had a progressive sperm motility < 50% with a density > 20 x 10(6)/ml (asthenozoospermia) and 13 had normozoospermia. MEUSC was performed on the same semen sample that was used for IVF on at least 100 spermatozoa after Papanicolaou staining at x 1250 magnification. Defects in the head, mid-piece and tail were counted separately, borderline forms were classified as abnormal and the teratozoospermia index was calculated for each sample. Of the spermatozoa in the asthenozoospermic group, 13.0% were judged as normal on MEUSC versus 19.8% in normozoospermia (P = 0.0013). The number of normal spermatozoa on MEUSC correlated with the progressive motility in asthenozoospermia (rho = 0.41, P = 0.0043). Defects in the mid-piece (P = 0.0004) and tail (P = 0.025) were more common, and the teratozoospermia index (P = 0.015) was higher in asthenozoospermic than normozoospermic samples. The parameters of MEUSC did not correlate with the fertilization rate. In asthenozoospermia, differences in fertilization rates were calculated for each cut-off value between 4 and 10% normal spermatozoa on MEUSC. A cut-off value of 6% gave the best statistical power. If > 6% of spermatozoa were normal, a median of 66.7% of ova were fertilized, compared with a median fertilization rate of 35.4% if < or = 6% of spermatozoa were normal (P = 0.022). The highest cut-off value still giving significant discrimination was 8% (normal MEUSC > 8%, median fertilization rate 66.7%; < or = 8%, median fertilization rate 35.7%, P = 0.028), and this may be used as the critical value for normal morphology in asthenozoospermia. It is concluded that despite a significant linear relationship between morphology using strict criteria and progressive motility, MEUSC is still useful as a predictor for fertilization in asthenozoospermia. In cases of asthenozoospermia with < or = 8% normal spermatozoa on MEUSC, micromanipulation should be considered.