calculating age of gestation

[cottonwood]

Okay, I finally figured out why some of you seem so far ahead of me gestation-wise, yet our due dates aren't that far apart. Well, there are two different ways of calculating this! One starts counting at LMP (last menstrual period) and the other at actual date of conception. Apparently the vast majority of care providers use the former (also known as Naegele's rule.)

So my only question is: why? Anybody know?

As an aside, here are some interesting thoughts about due dates:
http://gentlebirth.org/archives/dueDates.html

--Linda
(15 weeks from conception, 17 from LMP )

[JenInMpls]

This is what I know, Linda: Gestation is 10 moons - 280 days, or 266 days from conception (supposedly, assuming your follicular phase is 14 days long). Most doctors I have met go by your LMP, which really confuses them when it comes to me, because my follicular phases were really extended. So we go by my conception date, since we know that exactly.

Including my follicular phase, which they artificially shortened to make it fit into their formula, I'm at 20 weeks out of 40. Gestationally I guess it's 18 weeks the baby has been in there.

Why they do this, I have absolutely no idea. But I can ask my midwife for sure!

The Wise Woman Herbal says that the childbearing year is the 3 months prior to conception plus they 9 months of carrying.

This quote off of the page you linked makes me shudder:

What I was taught was to add 2 days for everyday over the 28 day cycle. For example, if a woman has a period every 30 days, you would add 4 days to the due date figured on the 28 day numbers. Does that make sense? I have found it to work pretty well. It works well the other direction too. For women that have shorter cycles.. Just subtract 2 days for every day under 28 days.

My cycles were always 35-40 days. GULP!

jen

[Mom2baldie]

So what do you think your EDD is Linda? I am 17 weeks past last menstrual period and about 15 from conception also. To be perfectly honest I say 17 weeks because I am excited and I want to be farther along.

[cottonwood]

I like knowing what age of gestation the baby is at (just for fun,) but I really don't see the sense of having a due date. However (shh, don't tell anybody,) according to a due date calculator I found on the internet, and given my LMP and the fact that my cycles had been monthly, my due date is supposedly Sept. 20. I figure I'll probably go before that actually, my pregnancies seem to getting shorter and shorter. (Now just watch me go into October. )

[sistermama]

My understanding of why the majority of the medical community calculates from LMP is because women are "incapable" of knowing when they conceived, but are considered reliable enough to know the date of their last period. I find this funny because I'm the type of person who NEVER knows the date of my LMP. I just don't pay attention to it. When I had to go to the health department to have a pregnancy test for my Medicaid eligibility, they wouldn't assign me a due date on paper because I didn't know my LMP and although I know my conception date exactly (Xmas eve), that wasn't good enough for them. :

[JenInMpls]

When Jo went to her physical and the dr asked her when her LMP was, Jo shrugged and said "I don't know, Jen usually keeps track of that stuff!"

I think I don't get any fuss about when I conceived because I conceived right down the hallway from where my midwife appts are taking place and all of my insems are in my chart. Ah, paper trail... they believe in it more than a woman's knowledge of her own body. sigh...

j

[CdnAloha]

I usually tell people IRL I am due in September and when they ask when I say "second-half". It could be anytime you know? I do know the exact guess date based on date of conception, LMP and a shorter luteal phase (12 days), but really none of that tells me the exact time or day the baby will be here.

There is a sign at my midwife's office that says "My baby will arrive at just the right moment." Now if only everyone went by that.

[chrissy]

I thought they started the count at 2 weeks before you ovulated/conceived because with the "normal" cycle that is when your body started preparing for the pregnancy. Do you know what I mean? Like, that is when the lining where baby implanted was formed and all that.

My body was all out of whack so I hadn't really had a period since before Noah was conceived. I know when I ovulated though so I just used that to figure out my "due date," which is September 28th. Most likely I won't have my baby until October though.