For artificial insemination, the sperm is prepared in the laboratory after being collected by masturbation, and then it is injected inside the woman's uterus through a plastic catheter, in the moment of the ovulation. Inside the uterus, the spermatozoa "swim" spontaneously towards the oviducts, where one of them will fertilize the ovum.

For in vitro fertilization, sperm is prepared in the laboratory and the eggs are retrieved from the woman's ovary using a puncturing needle guided by ultrasound. The oocytes are examined and put in contact with the spermatozoa in the laboratory. The spermatozoa will penetrate the membrane of the oocytes and fertilize them. The fertilized oocytes are put in a culture medium, and will start to divide their cells. They are now called zygotes. After approximately 2 to 3 days, the embryos are put into the woman's uterus. If they manage to fix on the endometrium (the uterus inner surface), pregnancy starts.