In the routine semen examination, there is an index called sperm motility, which is also called sperm vitality, and it is divided into four classes, such as A, B, C and D, according to the size of the motility. The sperm of class B has good mobility and moves forward in a straight line, but at a worse speed than class A. Class C sperm indicates average mobility, it moves forward and in a curve, and class D sperm has the worst mobility and can only squirm in place. But we should understand that the number of sperm in a male is huge every time he ejaculates, able to reach about 80,000,000-100,000,000, so not all sperm are of one level, but A, B, C and D. When judging male fertility, we mainly look at the number of A and B grade sperm. If the number of A and B grade sperm is >50%, it is considered to be normal for conception. If the percentage of C and D grade sperm is too large, it is diagnosed as weak sperm, which does not have the strength to move forward and has difficulty to cross the cervix to reach the fallopian tube to unite with the egg. However, the four types of motility, such as A, B, C and D, are relative. Through treatment, D-grade sperm can also be transformed into A-grade or B-grade sperm, so you should not be discouraged if you have weak sperm, but you can still actively treat and improve it.