Severe Oligo‐astheno‐teratozoospermia (Severe OTA syndrome) is a condition that includes low sperm numbers, low sperm motility, and abnormal sperm morphology. The definition of severe OTA is having <5 million/ml of sperm in a sample. Most cases of severe OTA are caused by idiopathic testicular abnormality or disorder. Genetic tests are abnormal in 7-10% of men with sperm counts of less than 5 million/ml. Severely impaired sperm motility may be caused by antibodies, chronic prostatitis, or rare recessive intrinsic defects of the sperm tail linked to sinopulmonary disease (for example, Kartagener’s syndrome or Young’s syndrome).
Treatment of severe OTA rarely improves the semen quality, but intracytoplasmic sperm injection (ICSI) is often successful even if only a few weakly motile spermatozoa can be isolated from the ejaculate. But still, performing ICSI in severe OAT patients is often a challenge as it is not always possible to find enough spermatozoa in these patients. Moreover, a major problem in severe OAT is the reduced chance for sperm selection regarding morphology. Fertilization rates of spermatozoa with several morphological defects are lower regardless of their source.