LMP vs. O date

[PiePie]

which do you use, and why? mine are 8 days different.

[ThreeBeans]

How for do you mean?

For example, my LMP was Oct. 31, and my ovulation date was November 14. So I am in my sixth week of pregnancy.....

[kettunainen]

I was told that most dates you'll find are geared towards LMP. Like "nausea usually sets in around week 5-7" means 5-7 weeks from the fiirst day of your last menstrual period. This is primarily because very few women actually know when they've ovulated, so it's easier to go from the first date of their last period and assume an extra 14 days for ovulation (which is a completely out-dated mode of determining ovulation, since fewer than half the women on the planet ovulate between cycle days 13-15, but that's how they do it).

So, as irritating as it is for me because I know when I ovulated (Nov. 1, around 10:30 - 11:00 am -- yay, mittelschmertz), I now use LMP dates just so that I don't confuse other people and so that I don't have to constantly do mental math when I look at development tables.

My dates are 17 days apart. Tomorrow (Monday), I'll be 8 weeks (LMP date/gestational age), and Wednesday, I'll be 6 weeks (ovulation date, fetal age).

[NVmama]

O date is more accurate, I would use it. Mine are 8 days apart too, because I ovulated on CD22. Your pregnancy is still calculated from two weeks before Ovulation, it just doesn't match up with your actual LMP dates. This is okay because this is the actual fetal age plus two weeks. If you choose a due date by your LMP, but you actually ovulated late, you run the risk of thinking you are more overdue at the end of your pregnancy than you actually are, which can lead to un-needed inductions or pressure to induce, which is stressful. Basically your LMP tells you a guesstimate of fetal age, your O date tells you the actual fetal age. Your pregnancy week should be fetal age plus two.

[Jster]

I'm not even positive I'll seek out medical care this time. But I know for sure that based on my history, I'll actually date myself one week off. Last time, I had a castor-oil induction at 42 weeks in order to preserve my homebirth, and I don't want to be faced with that time limit again. I'm much more worried about being pushed around at that end than on the other. So since I o'd on cd11, I would use LMP (gives me a few extra days) but actually I'll just use one week earlier than o as my "reported" LMP if I need to.

[Cujobunny]

I use my LMP (Oct. 28) so I am in my 7th wk of pregnancy.

It's weird though because then you're counting wks of pregnancy when you're not yet pregnant. That's how it works technically though, and if you're looking at stages of development.

[NVmama]

Originally Posted by Jster

Last time, I had a castor-oil induction at 42 weeks in order to preserve my homebirth, and I don't want to be faced with that time limit again. I'm much more worried about being pushed around at that end than on the other.

That's similiar to what happened to me. I induced with castor oil at 43 weeks, because I wanted to give birth at home and was under pressure because my "due date" was according to my LMP and I had not been charting. It resulted in a very hard labor and birth, my placenta ended up showing no signs of post dates and in hind sight I believe my baby was just not ready yet. This time I charted and know I O'd on CD22! No wonder I was "late"! It can be pure hell when you are overdue and people are telling you you need to induce or you will kill your baby, very stressful. This time I want to experience spontaneous labor.

[alegna]

Are you talking about how to count weeks or how to determine EDD? I determine the EDD that I believe by O date, because I run long cycles.

-Angela

[jandj+1]

I use my LMP for most purposes because that's the "language" that most people understand. So, by LMP I'm 5w3d.

But since I use NFP I know that I ovulated on cycle day 12. Thus, my baby is really 3w2d old.

[minkl]

if i knew my ovulation date and it was off by more than a few days, then i would make up a new LMP based on that, because the last thing you want to do is be pressured to an induction.
my mom was induced with me for being 3 1/2 weeks late...when in actuality, my mother said she had very long cycles (late ovulation) and i was probably barely overdue if at all. YOu don't want a baby coming out because doctors miscalculate

[PiePie]

my thoughts exactly. the first midwifery practice i spoke with uses lmp. i am going to interview them in more detail and also another. my concern is that if your labor is "postdated" (defined how?) you get bumped up from the birthing center (with, e.g., the nice tub) to the labor and delivery part of the hospital. that is what i want to avoid. dh thought i should lie about my lmp to get it 2 weeks behind the o date, but i have this romantic view of a midwife with whom i can share my innermost feelings, and somehow starting off with a lie seems bad.

[dantesmama]

I use my O date plus 2 weeks, so it's kind of my LMP if I ovulated on day 14 (which I didn't). I conceived on November 18, so at that point I was already 2 weeks pregnant, kwim? So I'm 6w2d, although my baby is really only 4w2d. It's just easier to use the way everyone else uses. I determined my EDD by using a EDD calculator that uses your actual O date, so I know my EDD is accurate. EDDs based on your LMP are usually inaccurate because so few women actually O on day 14.

[BoGiBoBo]

I haven't been to the midwife yet, but I am going to add a week to my LMP. I went late with the last 2 pregnancies, and I'd just as soon not stress about it later when they want to induce.

[nakagain]

I prefer my ovulation date so I'm not sad when I pass my edd. I ovulated on day 20 so its a week past my edd date and I have longer cycles. According to LMP I'm about 5.5 weeks but according ovualtion I'm 4.5 weeks and with a short LP factored in I'm 3.4 weeks. who really knows besides the fact I'm pregnant.

I'm so glad i understand my body and can be 42 weeks with LMP and know for certain I'm not really 42 weeks.

Basically end of Aug. begining of Sept.

[Emma's_Mommy]

i took my O day (i o early) and counted back 14 days and told my OBGYN that was the day of my last period (even though it wasn't) so that way the due date is accurate as possible!

I have small babies and b/c of my bladder condition i will be having a repeat c-section and i want to have it as close to 37 weeks as possible to avoid any extra damage to my bladder