Wow, I really wouldn't have expected someone to try to disprove my comment. Lol, I never said there was a fetus at day one. I specifically said started as an egg. Before the egg is released around day 14, the egg is maturing in preperation to be released.
I am so very sorry for accidently saying the egg is released on day 1. It is not released, it is simply the one specific egg that is being prepared to be released.
Day 1 isn't when the egg is released (much less when a 'fetus' is created... that doesn't happen until the end of the 10th week when the embryonic stage ends). Day 1 is the first day of the menstrual cycle. The egg is released at ovulation which is generally around day 14, but can be earlier or later. Conception can happen the same day as ovulation or up to several days later. It is impossible to determine exactly when conception occurs, but it is hard to mistake the first day of a period. Since most cycles are about the same length, counting from LMP gives a good starting point to count from.
You are not pregnant for the first 2 weeks but it is counted in pregnancy bc pregnancy is the life of that fetus- which started as an egg, so day 1 is when the egg was released, around day 14 is when it is fertilized.
You aren't actually pregnant fir the first 2 weeks, because it is counted from the first day of your last menstrual period. Conception doesn't actually happen till about 2 weeks after that. It is just easier to calculate that way, since most women do not know when they ovulate.