Since the process of ovulation, or the release of a mature egg, occurs around the 14th day of the cycle starting from the LMP, you are not pregnant during the first two weeks yet. Pregnancy occurs when the sperm successfully fertilizes the egg.

However, it is very hard to pinpoint the exact day when sperm meets egg. For this reason, the start of pregnancy is counted from the first day of the woman's last menstrual period (LMP).

Counting from the LMP, most women are pregnant on an average of 280 days or 9 months. For consistency, health care providers usually use this method of calculating the due date.