Fertilization

About once a month, an egg is released from one of a woman's two ovaries (ovulation). The egg then enters the nearby fallopian tube. During unprotected sexual intercourse, sperm that is ejaculated from the man's penis may reach the egg in the fallopian tube. Fertilization occurs if one of the sperm cells penetrates the egg. The fertilized egg usually travels down the fallopian tube to the uterus.