Calculation of how many weeks pregnant

[m3lanie]

I am truely confused to hell about how they calculate the weeks someone is pregnant. They say I am 6 weeks pregnant because that is how long ago my last menstral period was but I concieved 3 weeks ago... so how can one get away with stating I'm 6 weeks pregnant  when that's impossible? I don't get it. 3 weeks ago my OPK tested positive and so then my partner and I BDed on either side of both positive OPK days and then 8 days later i tested a faint positive on a pregnancy test. So how can they claim that I'm 6 weeks when it's only 3 weeks? This in turn makes things even more confusing because when I look at Week by Week development of my baby, online I wonder well do i look at the 3 weeks or do I look at the 6 weeks?  Fact = my baby has only been developing for 3 weeks not 6. My Pregnancy tracker is even wrong on this site.

Anyone know how to  explain this one? lol

[jovanj]

ok...lol thank u!! it was just very confusing but that did help so thank u very much :) i will prob have more questions along the way lol thanx again!!!...

[adgal]

It doesn't really make sense I know.  When dating your pregnancy they start counting 40 weeks from the first day of your last menstrual period.  So even if you ovulated 14 days after the first day of lmp, they would still count backwards almost 2 weeks.  So if your Dr. is telling you you are 6 weeks, you probably conceived about 4 weeks ago.  They do this because women ovulate on different days, and there is no exact way to tell when you conceived.  Hope that helps.

[jovanj]

i had my doc say i was over 6 weeks when i only had sex 4 weeks ago?? that doesnt make sence, idk can anyone explain that? lol

[kat9673]

The way u calculate your due date is the first day of your last period. You add 7 days to that and then the month you subract three months. So for example last period was Feb. 7, 2009
You will add 7 to 7 which is 14 and from Feb. subtract 3 months, which would be Feb. Jan. Dec. So your due date is calculated as Nov. 17, 2009 and you count your weeks from that... I hope that helped a little bit.... 40 weeks total and just count forward from your due date.

[SoCalTricia]

Sounds like you probably have a longer cycle than the standard 28-day, and ovulated later that two weeks past your last period. But, like the others said, the standard every doctor goes by is your last period. The only way around it, really, is to tell the doctor your period was two weeks before conception. I'm not sure I'd do that, if I was absolutely sure when my period was. Did you tell your MD when you ovulated?

Tricia

[adgal]

My understanding is that they do it this way as a generalized way of dating things.  40 weeks from first day of LMP.  So really, you re only pregnant 38 weeks.  Most women do not track their ovulation, many don't have a clue when it was.  Even if you track it, you can easily be off by 3 or 4 days as sperm lives a while in a fertile enviroment.  This drives my DH batty..lol.  Anyway, docscaf is absolutley right, you would be looking at the 6 week development.  

[docsaf]

I don't know why they use it, but it is the norm to calculate how many weeks pregnant a person is by the day of their last period. But even this is based on a 28 day cycle. I think that it was easier for doctors to use day of last period instead of guessing when a person O'd. With the PK, we know now, but I'm guessing 40+ years ago, many women weren't sure when they O'd but knew when their last period was.

When you look at the week by week development, use 6 weeks unless it states "week from conception". If it states anywhere weeks from conception, use 3 weeks.

Good luck with your pg!