Quantified ultrastructural study of spermatozoa in unexplained failure of in vitro fertilization

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Abstract
Failure of in vitro fertilization or very low cleavage rates may occur even though oocyte and semen parameters seem satisfactory. Quantified ultrastructural study of spermatozoa was performed in such cases of failure (n =6) or low cleavage rate ( n =4). Through 1 to 11 retrievals, the number of inseminated oocytes ranged from 14 to 145. The results were compared to those of six fertile men. Quantification was achieved by cataloguing cell defects of the spermatozoon heads and mid-/principal pieces of the flagella. Using the data from each specimen, the percentages of total cellular abnormalities in the head/mid-/principal pieces were established. At the level of the head overall percentages for six groups of defects were determined. The overall percentage of combined head abnormalities, defined as the presence of at least three of these six defects on the same spermatozoon head, was established. Statistical differences among control and patient groups were analyzed by nonparametric Mann—Whitney Utest. The percentages of anomalies of the midpiece and of the principal piece were not significantly different between patients and controls. Motility assessed by spermogram was considered “functionally uncompromised.” In eight patients the percentage of cell alterations of the head (93–100 vs 77.3 ± 6.4%) and the percentage of combined anomalies of the head (78.1–100 vs 60.8 ± 8.5%) were significantly different between patients and controls. In two cases, the percentages established for all head parameters considered were not globally different from those observed in controls. Thus in 8 cases of 10, electron microscopy with quantified analysis supplied valuable evidence about the poor quality of these sperm samples judged as normal under light microscopy and may provide an explanation for their impaired fertilizability. In the two other cases the fact that the sperm appeared to be ultrastructurally normal does not rule out functional sperm pathology. Alternatively, defects in the oocyte may also account for unexplained failures of in vitro fertilization.