Pregnancy depends on a healthy egg, healthy sperm, and favorable cervical fluid. For birth control to work, the process of conception must be stopped at some point along the way. During sexual intercourse, sperm are ejaculated through the man's penis into the woman's vagina. In the presence of certain cervical fluid conditions, some of the sperm move, guided by the cervical fluid, through the cervical opening, through the woman's uterus, and into the fallopian tubes. It is also possible for sperm to be deposited in or near the lips around the vagina during ejaculation, even without intercourse, and to travel up the vagina from there. If the sperm encounter an egg in the outer third of the fallopian tube, one may join with the egg. The process of an egg and a sperm uniting is called conception or fertilization. The fertilized egg takes several days to travel down the fallopian tube to the uterus, where, after one and a half to two days, it may implants in the uterine lining and develops over the course of the next nine months.

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Our Bodies, Ourselves: A New Edition for a New Era
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.