How does pregnancy happen?
The menstrual cycle causes the ovary to make an egg that is released by the ovary (ovulation). The fallopian tubes make a wave like action and sweep the egg into the tube where it can meet with sperm. The egg must be fertilized within 24 hours. Sperm can live up to 5 days in the uterus waiting for an egg to be released or sperm can swim up to meet an egg within 5 minutes of ejaculation. Fertilization happens when an egg cell and a sperm cell join to make an embryo. The embryo then travels to the inside of the uterus where it grows into the lining of the uterus (called implantation), and it is now called a pregnancy. Once the embryo is implanted it makes a hormone called human chorionic gonadotropin (hCG) which is what makes the pregnancy test turn positive. The hCG hormone also goes to the ovary and makes the ovary continue to make progesterone and estrogen to support the lining of the uterus and the pregnancy. Eventually the placenta (what may later be called the afterbirth) will take
