one or more variables below the 5th percentile, and confers a chance of pregnancy occurring naturally through vaginal intercourse within two years similar to people with mild endometriosis. Collection methods Methods of semen collection include masturbation, condom collection, and epididymal extraction. The sample should never be obtained through coitus interruptus as some portion of the ejaculate could be lost, bacterial contamination could occur, or the acidic vaginal pH could be detrimental for sperm motility. The optimal sexual abstinence for semen sampling is two to seven days. The most common way to obtain a semen sample is through masturbation and the best place to obtain it is in the clinic where the analysis will take place in order to avoid temperature changes during the transport that can be lethal for some spermatozoa. Once the sample is obtained, it must be put directly into a sterile plastic receptacle (never in a conventional preservative, since they have chemical substances such as lubricants or spermicides that could damage the sample) and be handed to the clinic for it to be studied within the hour. There are some situations in which a special obtaining is needed, such as retrograde ejaculation, neurological injury or psychological inhibition. Depends on the situation we can use different methods such as special preservatives, electro-stimulation, vibro-stimulation, etc. Parameters The parameters included in the semen analysis can be divided in macroscopic (liquefaction, appearance, viscosity, volume and pH) and microscopic (motility, morphology, vitality, concentration, sperm count, sperm aggregation, sperm agglutination, and presence of round cells or leukocytes). The main three parameters of the spermiogram are the concentration of the spermatozoa in the semen, the motility and the morphology of them. This analysis is important to analyse the fertility of a man, but even in a perfectly fertile man is very difficult to find normal spermatozoa, indeed, on the average of fertile men, only the 4% of their spermatozoa is normal in every parameter, while the 96% is abnormal in at least one of them. Sperm count Sperm count, or sperm concentration to avoid confusion with total sperm count, measures the concentration of sperm in a man's ejaculate, distinguished from total sperm count, which is the sperm count multiplied with volume. Over 16 million sperm per milliliter is considered normal, according to the WHO in 2021. Older definitions state 20 million. A lower sperm count is considered oligozoospermia. A vasectomy is considered successful if