This refers to abnormal sperm morphology. A normal appearing sperm has an oval elongated head with the dark staining nucleus (DNA) and 1 or 2 empty spaces (vacuoles).The head is connected to the tail by a midpiece which has a neck. Under the microscope at least 4% of sperms should appear normal. However, this is highly subjective as it depends on the person looking under the microscope. Toxins, infections and Varicoceles again contribute to abnormal sperm morphology.