If a baby is 7 weeks old, does it mean it was conceived 5 weeks ago?

Baby or fetus? It takes 40 weeks +/- to bring baby from conception to due date. Your stage is usually measured from your last menstrual flow will estimate conception 2 weeks after that date because that's when the egg is most likely to be fertilized. If your pregnancy is 7 weeks along, you conceived 7 weeks ago. Later in your pregnancy, the growth of the fetus & other measurements may suggest a different date.