How does Pregnancy Begin in a Woman's Body?

A woman’s first menstrual cycle indicates that she has entered her fertile years.

• Every month, women in their fertile years go through a menstrual cycle. The average length of the cycle is four weeks.
• During every cycle, an egg in one of the two ovaries reaches full maturity and is released into one of the two fallopian tubes. 
• The release of the egg, which is called ovulation, usually takes place at the middle of the menstrual cycle.
• Once released, the egg begins to travel through the fallopian tube toward the uterus. 
• The egg lives for about 12 to 24 hours from the moment of its release. During this period, if a sperm penetrates the egg, it gets fertilized.

Once the egg reaches the uterus, one of two things can happen:

• If the egg has been fertilized, it attaches to the uterine wall and pregnancy begins.
• If the egg hasn’t been fertilized—or if it is fertilized but doesn’t manage to attach to the uterine wall—it gets expelled from the body in the menstrual flow. In this case, no pregnancy occurs.