We often encounter men in male clinics who come for routine semen testing because of inevitable miscarriage or fetal abnormality, so we have to ask, can semen analysis determine fetal abnormality? Will abnormal sperm give birth to a malformed fetus? Can a poorly motile sperm conceive? Nowadays, many patients, and even many doctors, take it for granted that bad sperm will conceive a bad fetus and that miscarriage is caused by bad sperm. Before answering the above question, let’s understand the process of sperm to conceive. The spermatozoon has an oval head and a long tail. In front of the spermatozoon head, there is a thick-bottomed bowl-like substance, which we call the acrosome, which dissolves the cell membrane of the female egg and allows the spermatozoon head to enter the egg and unite with the egg. The active sperm tail, like a high-speed propeller, propels the sperm forward. Through a special identification system, the sperm travels from the woman’s vagina, through the cervix, uterine cavity, fallopian tubes and, after a long journey, finds the egg, during which deformed and poorly active sperm are eliminated and only about 10% of good quality sperm reach the egg and unite with it, then releasing the acrosome enzyme, which dissolves the egg’s cell membrane. The egg cell membrane is dissolved and the head of the sperm enters the interior of the egg, while the egg cell undergoes rapid structural changes to prevent a second sperm from entering the egg. Only sperm with normal morphology and vitality have the possibility to conceive, while those with deformities and poor vitality are eliminated in the process of conception, so how can they cause an abortion? How can it be possible to give birth to a deformed fetus? According to many people, the process of sperm conception becomes a democratic election, and the majority of deformed and poorly energized sperm will conceive, which is biased. However, on the other hand, the chromosomes carried by a sperm with normal morphology and viability are not necessarily normal. It is possible that it carries one or several abnormal chromosomes into the egg to combine with the chromosomes in the egg and may lead to miscarriage or abnormal babies, while the woman’s egg may also carry abnormal chromosomes causing miscarriage and abnormal babies. In clinical practice, we can only see the number, shape and vitality of the sperm, but not the chromosomes within the sperm. Therefore, semen analysis can only determine the fertility of a male, but not the fetus.