Follicle Stimulating Hormone (FSH) starts the whole process off at the beginning of the cycle. It is a hormone produced by the pituitary gland, a small stalked structure at the base of the brain. FSH does what it says – it stimulates follicles - the structures in the ovaries that house eggs – to stimulate the egg to mature to the point at which it is ready to be fertilized. The follicle and egg are “ripe” at about mid-cycle, usually 14 days after the start of the last period. Just before this point, a spike in the level of estrogen, a hormone produced by the ovaries, followed by a spike in the levels of LH and FSH from the pituitary, cause the ripe follicle to complete its maturation process and rupture in a process called ovulation. The estrogen and progesterone also help to stimulate the development and growth of the uterine lining. The ripened egg then floats away from the ovary and down the fallopian tube to the uterus. At any point of this journey, which usually takes a few days, it can be fertilized by a single spermatozoa. When a fertilized egg implants in the developed uterine lining, a pregnancy results. In the meantime, the ruptured follicle (“corpus luteum”) continues to produce progesterone and estrogen to stabilize the lining of the uterus in preparation for implantation of the fertilized egg. If a fertilized egg implants, the placenta, a vascular structure that nourishes the embryo, maintains the production of estrogen and progesterone. If an egg is not successfully fertilized and/or implanted, estrogen and progesterone levels decrease, causing the uterine lining t...