Oligasthenoteratospermia is when three parameters of count, motility and shape of sperms are low and abnormal.
Oligospermia is when the sperm count is low in the ejaculate. Sperm count is consider low if the number of sperms is less than 15 million in one millilitre of semen.
Asthenospermia: This is when the sperm “motility” is reduced. Motility is one of the important paraments of sperm quality, therefore low motility mean low quality of sperms and reduced chance of natural conception. If the count is quite high , the effect can be negated as the absolute number of motile sperm can be normal. The absolute number of the motile sperm is called Sperm Motility Index which is more important than only the percentage of motile sperm. The Motility index can be calculated by percentage of motile sperms (% moving forward) X sperm concentration. This is more correlated with chance of pregnancy rather than the percentage of motile sperms.
Teratoseprmia is when the abnormally-shaped sperms constitute more than 96 % of the sperms. The abnormality may involve the head or the tail of the sperms. the tail is responsible for movement of the sperms and head is for penetration to egg. Therefore too much abnormality can have a negative effect on the male fertility.