A normal couple needs the following basic elements for a normal pregnancy: 1. Normal eggs (from the woman) and normal sperm (from the man). A normal woman normally releases one to two eggs in a menstrual cycle, while a normal man can release 200-300 million sperm in one ejaculation. 2. Normal reproductive ducts. The female internal reproductive system includes the vagina, uterus, and both adnexa (ovaries and fallopian tubes) The male reproductive system consists of gonads (testes), transport ducts (epididymis, vas deferens, ejaculatory ducts, male urethra) and accessory glands (seminal vesicle gland, prostate gland, urethral bulb gland). 3. The sperm and egg can unite normally (fertilization) 4. The endometrium is receptive, which means that the development of the endometrium should be synchronized with the development of the embryo and be able to accept the embryo. Now let’s connect this physiological process. After intercourse, sperm pass through the vagina and reach the uterine cavity and the abdomen of the fallopian tube, while after the ovary discharges the egg, the umbrella end of the fallopian tube catches the egg like a hand and transports it to the abdomen of the fallopian tube to wait for the sperm. After the sperm and egg have been fertilized and turned into an embryo, the fallopian tube transports the embryo to the uterine cavity where it settles and develops. That basic pregnancy process is complete. A mistake in any of these steps will affect the process of pregnancy and cause infertility.