Female reproductive system:
- Ovaries: they are responsible for the storage of the eggs and production of hormones.
- Fallopian tubes: site of fertilization, where the egg meets the sperm. The tube carries the egg to the uterus.
- Uterus: this is the organ that receives the fertilized egg and where pregnancy develops.
Women with regular cycles menstruate every 26-30 days. Halfway through the cycle (around the 14th day) ovulation occurs. Only one egg matures under the influence of hormones and is released from the ovaries every cycle, after which it reaches the Fallopian tube. This is where the sperm meet the egg and fertilization takes place.
Ovulation and pregnancy require the presence of four important hormones in the woman’s cycle: the FSH and the LH are released by the hypophysis (a gland located in the brain), and estrogen and progesterone which are produced by the ovaries. The physician works with these hormones in the majority of fertility treatments.
As of the first day of menstruation, the hypophysis begins producing the Follicle Stimulant Hormone (FSH), which as the name explains, stimulates the growth of the follicles inside the ovaries. Each follicle contains one egg. The follicles produce estrogen, a hormone in charge of preparing the uterus for a future pregnancy. Halfway through the cycle (around the 14th day after menstruation), the hypophysis produces another hormone called LH which, in turn, induces ovulation. Soon after ovulation occurs, the follicle produces another hormone, the progesterone, which also helps prepare the uterus to receive a possible pregnancy.
If sexual relation takes place during the ovulatory period, sperm is deposited in the vagina and swims up reaching the uterus and the tubes where only one will penetrate the egg, thus ensuing fertilization and the formation of a future baby.