# Don't understand how pregnancy calculator calculates estimated due date

 3 If I visit a pregnancy calculator such as this one, and enter May 25th 2010 as the first date of the last menstrual period, it says (as of today) that the gestational age is 7 weeks. However, today (July 13th) is exactly 7 weeks past May 25th. How could the baby have been conceived on May 25th 2010 if my wife was menstruating on that date (and continued to menstruate for about a week past this date)? asked 14 Jul '10, 06:55 Jimmy 61●2●3 accept rate: 0% please accept an answer if you think your question got answered. (19 Jul '10, 08:17) Fisherman

 7 that is because of the calculation that is used. If you say that a pregnancy is 40 weeks (or 280 days), this is from the date of the last period till the birth. But the actual conception happens in week 2 of the pregnancy if you count it like this. Check this article: http://www.whattoexpect.com/pregnancy/week-by-week/weeks-1-and-2.aspx Believe it or not, the countdown to delivery day begins in week one — even though your egg and his sperm haven’t even been in the same room (or womb!). So how can you call this your first week of pregnancy if you're not even pregnant? Grab your calendar and take note: Because it's extremely hard to pinpoint the precise moment pregnancy begins (i.e., when sperm meets egg), most practitioners use the first day of your last menstrual period (which you're having right now) as the starting line of your 40-week pregnancy. Confused? Consider it a head start — you're clocking in roughly two weeks of pregnancy before you even conceive! answered 14 Jul '10, 10:47 Fisherman 599●3●5●11 accept rate: 8%
 1 Also most calculators presume that women have a 28 day cycle and ovulate on day 14, this as we know is not allways the case. I for example can range from a 28 - 34 day cycle and only have a 10 day luetal phase, so when i go for a dating scan my EDD is normally put back by at least 10 days. answered 16 Jul '10, 07:02 Phil Seller 2.5k●1●15●25 accept rate: 9% that's why some calculators ask for the avarage length of the cycle. (16 Jul '10, 07:45) Fisherman
 0 The First sign of pregnancy is Missing period. BUt my pads are still ON, doctors says i am pregnant. How? 2 weeks pregnant answered 01 Nov '12, 05:51 Rubysyed 11●1 accept rate: 0%
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