How can a doctor count you as being 2 weeks pregnant from the first day of your last menstrual period?

http://www.babycenter.com/pregnancy-calendar/getinfo?_requestid=356370
I am wondering how a doctor can count your pregnancy from the first day of your last menstrual period. I always though the doctor counted from the day of conception. So when you take a pregnancy test your already 3-4 weeks pregnant. But some women who take a pregnancy test get a negative result which means they were never pregnant to begin with. Forgive me for my ignorance it’s just I am wondering how doctors come up with that crazy idea to count a pregnancy from the first day of your last menstraul period and WHY the do it this way. It just doesn’t make much sense to me. Like for me I put my date of my last menstrual period in to the above calender and it said I’m 2 weeks pregnant which I don’t see as possible as I can’t take a test until May 11th which would mean I’d be 4 weeks pregnant by then. If any doctors use this site or anyone who has knowledge of this please answer. Thank you.

That does cause confusion among many expectant women.

Pregnancy is counted from the last menstrual period because often that is the only definite. Gestation is counted from conception (which sometimes is guessed). But when your doc talks to you the numbers will be weeks of pregnancy.

You are right, it doesn’t make any sense that you are two weeks pregnant when you conceive. But, its not like you can change the system.

Here’s more about it http://birthingnaturally.net/pregnant/issues/duedate.html

Good Luck

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