The start of your pregnancy begins before conception
Week 1: Understanding the differences between gestational and fetal age
The 1st week of pregnancy is called preconception, because it actually begins with the start of your last menstrual period. Why? It's hard to pinpoint exactly when your egg becomes fertilized, but the date of your last cycle is a more accurate starting point.Your doctor will calculate your due date by counting 40 weeks from the start of your last menstrual period.
This is called the gestational age, and it's...