According to the World Health Organization (WHO), the man who only has a sperm count below 20 million sperm per milliliter of semen, it is difficult to conceive. Why does it take millions of sperm that can fertilize if only a single cell? This is due to travel from the vagina into the fallopian tubes to meet the egg is very difficult.
In fact, the egg is able to survive and reach the fallopian tubes, which still have to fight again to fertilize the egg because the egg is covered with a thick layer that makes the process of fertilization is more difficult. Experts believe it is a difficult stage that natural selection so that only healthy sperm cells are able to fertilize. So babies will be born healthy.