How Does Pregnancy Happen
Once a month, a woman releases an egg from one of her ovaries. The fallopian tube takes the egg from the ovary toward the uterus (or womb).
During vaginal sex between a woman and a man, the man's penis ejaculates in the woman's vagina. That ejaculation shoots millions of sperm up into the woman’s vagina, where they race through the cervix (the opening to the uterus), then the uterus and into the fallopian tubes hoping to find an egg. If they find one, fertilization may occur.
Each month a woman's brain sends out hormones that cause changes in her uterus. At one point in the cycle, her body creates a potential home for the fertilized egg in the wall of her uterus. A woman can only become pregnant during the days when the uterus is ready. If the fertilized egg doesn't attach during this part of her menstrual cycle, the uterine lining is expelled from her body during her period.
Pregnancy starts when the fertilized egg attaches to the uterus. Once it's attached, the egg grows into an embryo and eventually a fetus.
A woman's body goes through many changes during pregnancy. She gains weight to help keep the fetus growing and protected. She produces more blood, so that there's enough for two bodies instead of one. Toward the end of her pregnancy, a woman's breasts enlarge and get ready to produce milk. And in preparation for the final delivery of the baby, some muscles and ligaments (ligaments attach muscles to bones) relax, so that the baby has room to get out. The entire process, from ejaculation to delivery, takes about 40 weeks.
Acknowledgements: This fact sheet was originally developed by our friends at nativestand.com