A woman's due date is calculated from the first day of her last menstrual period. Conception occurs two weeks from that day -- that's when you're truly considered to be pregnant! Millions of sperm swim upstream on the quest to fertilize an egg. Only one successfully penetrates the egg, forming the genetic makeup that will determine the sex, physical appearance, intelligence, and personality of the baby. Watch the ovulation process occur by clicking on the video above. Chances are you have no idea you're pregnant yet -- but your body is already hard at work.
Egg, sperm, and fertilization
Egg, sperm, and fertilization (video) | Khan Academy
For a women to conceive, her egg has to be fertilized. Even when the woman has a healthy egg and the man has healthy sperm, it can still be difficult to conceive. The amount of time that it takes for sperm to fertilize and egg can vary significantly from person to person or case to case. To have an egg fertilized successfully, you need to have a high enough sperm count. Although a single sperm can in theory fertilize a sperm, a higher sperm count increases the chances.
Your Baby's Journey from Conception to Birth