Fireworks occur at the moment you become pregnant. (Literally – Read about it HERE)
But that is not considered the first day of your pregnancy. For an easy formula to determine an approximate due date, birth workers consider the first day of your last period as the beginning of pregnancy. This is the day the first trimester begins.
The body preps the uterine wall for a healthy attachment of a fertilized egg. Ovulation takes place, and the egg is penetrated by a sperm. This action is the moment of conception. Every day after this is important, as that tiny egg is going to develop into a baby!