Key Features

• For ease in viewing, the sperm are represented here as much larger than they are. In reality, the ovum is more than 1,000 times larger than each sperm. Although there are only a few sperm represented in the animation, in real life, thousands of sperm at a time will be attempting to fertilize the ovum.
• The animation covers the second half of the menstrual cycle. A menstrual cycle is from the first day of one period to the first day of the next period. During the first half of the cycle (happening before the animation begins) the ovum matures inside a special space in the ovary called a follicle. At the midpoint of the cycle (usually day 14 for women who have a 28 day cycle), the ovum is released from its follicle, and begins the journey down the fallopian tube to the uterus.
• Since this woman had had sex within the last several days, there are be sperm waiting to fertilize the egg. That's because sperm can live inside a woman for 3-5 days or more. That's why you do not have to have sex on the day you ovulate in order to get pregnant. The egg can last for 24 hours without being fertilized. If you have sex within 24 hours of ovulation, you can get pregnant.
• The ovary and the tube are not connected, they are simply near each other. The ovum is swept into the tube by the fimbria, the waving finger-like projections at the end of the tube.
• The endometrium (lining of the uterus) is growing in preparation for nourishing a fertilized egg.
• Fertilization usually takes place within the fallopian tube. The fertilized egg continues drifting down the fallopian tube to the uterus. During that time it divides again and again.
• By the time it reaches the uterus, it is a ball of cells. It must implant in the wall of the uterus where it will grow and develop for the next 9 months.
• Implantation usually occurs 6-8 days after ovulation. That would be between days 20-22 in a 28 day cycle. Some women will notice a spot or two of blood after implantation. This is called implantation bleeding. Most women do not have implantation bleeding.
• Once the ball of cells has implanted in the wall of the uterus, it can release HCG (pregnancy hormone) into the mother's bloodstream. Until then, there is no pregnancy hormone in the mother's bloodstream and no way to know if she is pregnant. A blood pregnancy test will become positive within a day or two of implantation. A home pregnancy test (which measures the amount of pregnancy hormone which has made it into the mother's urine will not become positive until several days later. Most home pregnancy test are not sensitive enough to detect pregnancy hormone until the day you expect your period.