Normal Fertility Cycle

To get a good understanding of how fertility treatments such as IVF and IUI work, it is best to have an idea of typical egg development and fertilization.  Please take a look at the images and descriptions, as they will give you a good baseline to understand this complex process.

During the normal course of a menstrual cycle, a woman begins the cycle with a crop of developing oocytes (eggs,) which mature over the course of the menstrual cycle.  At approximately day 14, only the best egg is left, as the body is pretty smart and only lets the strongest egg finish the maturation cycle.  See the figure below to see where the oocytes (eggs) develop, they are the small gray circles on the ovaries.

Once the egg has matured, it is time for fertilization.  The sperm travel up the vagina, through the cervix and into the fallopian tubes.  Fertilization typically occurs in the fallopian tube and the fertilized embryo travels down the fallopian tube and implants in the uterus.

The fertilized embryo typically implants in the top part of the uterus, where it begins dividing and nine months later, delivery occurs.