Pregnancy and childbirth is a natural human physiological process and the most basic material basis for human reproduction and the maintenance and development of society. There are many factors that influence pregnancy, but the most basic ones are summarized in four points: healthy egg cells, sperm cells, fallopian tubes (the site of fertilization), and the uterus (the place where the fetus is conceived). As mentioned in previous articles on menstrual physiology, the ovaries have two main functions: first, to secrete sex hormones; and second, to periodically develop and occlude the follicles within them. For most women, a normal mature egg occurs and is expelled each menstrual cycle, and ovulation usually occurs about 14 days before the next menstrual period. It is important to emphasize that it is perfectly normal to occasionally experience one or two instances of non-ovulation and there is no need to be overly concerned. Sperm production refers to the entire process of male germ cells becoming mature sperm from undifferentiated stem cells, i.e. spermatogonia. The volume, liquefaction time, malformation rate, density, viability and activity rate of semen are initially determined by routine semen examination. The process of fertilization is like this: when an egg is mature and expelled from the ovary, it is picked up by the umbrella of the fallopian tube and incorporated into the fallopian tube, where it meets with the sperm that swims into the fallopian tube from sexual ejaculation into the female uterine cavity, so fertilization occurs in the fallopian tube. The fertilized egg starts to cleave, one cell becomes two, two becomes four, and starts to swim towards the uterine cavity, finally planting itself in the fertile soil of the uterine cavity and slowly differentiating and developing into a fetal placenta. If the fallopian tubes are not open and there are narrow places, the fertilized egg after division increases in size and cannot reach the uterus through the fallopian tubes and is retained in the fallopian tube for pregnancy, which is called ectopic pregnancy, and 95% of ectopic pregnancies occur in the fallopian tubes. If the fallopian tube is inaccessible, the egg and sperm cannot meet and fertilization is impossible, so pregnancy does not occur. This method involves removing the egg cells from the ovary through vaginal puncture when the follicle is mature, incubating the sperm and egg cells together outside the body to form a fertilized egg, and then transplanting it into the uterine cavity, which does not require passing through the human fallopian tubes. In order to increase the success rate, it is usually necessary to stimulate the ovaries with drugs to obtain multiple eggs to increase the success rate, and the extra fertilized eggs can be frozen for the next time (if unsuccessful).