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Why do doctors change the due date?

post #1 of 25
Thread Starter 
I never understood this. Just because the baby is measuring at 6 weeks when you know you're 7 weeks, why do they change the due date? Why don't they just say, "Gee, she's measuring a little small for 7 weeks, but no worry, we're not that far off."

My doc changed my due date from April 24 to April 30. That's a full week's difference. Yet, I was in her office the day I ovulated cuz we had an ultrasound and saw it happening, that's how we knew when to do the dance. Are they trying to say that ovulation was somehow put on hold for a week? Or should they really be saying, "your baby is measuring small for the due date?"

What do you guys think?
post #2 of 25
Personally I would fight your Ob on this. Due dates are more important than you may initially think- if you go past.
My daughter was born at either 41 or 42 weeks. I was a nervous wreck thinking I was going to get risked out of midwifery care and my homebirth. I had no idea the importance of that due date.
Of course you're going the other way but there's dangerous in that to. Like if your Ob decides you need a c-section for some reason- you want to give your baby all the time it needs to cook.
If you know when you ovulated or if you know (like I do) when implantation happened. Tell your Ob that! At least make sure it's noted somewhere that there are two possible due dates- it might be important later on.

But that's just my opinion!
post #3 of 25
It depends. US's between 6-7 weeks are pretty accurate at determining due dates (they're NOT as accurate during other weeks, especially later in pregnancy). I would be more concerned if your doc thought you were due EARLIER than you thought, because then there's a greater risk of induction. How sure are you that you have the date right?
post #4 of 25
Question - did she say this because of the ultrasound? Did you have a dating ultrasound done? It wasn't clear from your post. If she was just looking at your belly, then I'd stick with your EDD if you're sure of it. It's way too early to tell from just looking at the belly!
post #5 of 25
If you know the exact day you ovulated....which you do, obviously, tell the doctor to fly a kite LOL. There is no more accurate way to figure out a due date than by ovulation.
post #6 of 25
i've encountered this very issue today. I was pretty sure I was 7 weeks but in an ultrasound they said that I measured 6 weeks and that the heartbeat was too slow to be 7 weeks. I don't know how I could be a whole week off. I am worried that the baby just isn't developing I think the confusion is in that they judge your dates by your last period and not necessarily when you actually ovulated. I know it has been 7 weeks since my last period but I guess I don't know exactly when I ovulated. Does that make sense? Could it be that I ovulated a week later than what is typical? I am worried now that something is wrong, I didn't like hearing that the heartbeat was weak. I am scheduled to do another ultrasound in a week to check dates again.
post #7 of 25
Thread Starter 
Well here's the thing.

On July 31 I had a pretty in depth ultrasound. And the tech said, "Oh your follicle is 22mm. Women ovulate when their follicles are between 19 and 24 mm so I'd say you're going to ovulate in the next 12 to 24 hours." That's when we did the dance, although truth be told, we were doing the dance every couple of days that whole rest of the week cuz we were on a lovely vacation with lots of time for dancing.

So I have assumed that I ovulated on August 1 or at the latest, August 2.

But this new due date puts my ovulation at August 7. Do you guys this it's possible that I really did ovulate a week later than the technician thought? My evidence is based on what she told me but she's not a doctor.

I got a positive pregnancy test on August 16, so that would be only 9 days after my supposed ovulation.

They determined due date with the ultrasound, the heavy duty one, not the one the nurse practitioner brought in. She said I was measuring at 6weeks when I thought I was at 7 weeks.

What do you guys think?
post #8 of 25
sorry I didn't mean to hijack, it is just that I was about to post the same exact thing! It sounds like you have a better idea of the ovulation times than me though. How long does the egg survive before fertilization? I think I heard like 24-48 hours but I could be totally wrong. That could add a few days if that were the case. Did your ultrasound find a heartbeat? This seemed to be the main concern of the nurse that did mine....then again it took her and three other people to figure out how to just turn the machine on...
post #9 of 25
Well, just because the follicle was that size doesn't mean it released when she thought, say it took 48 hours more instead of 24, and say perhaps 48 hours more to fertilize, that would put you 4 days earlier than you thought...pretty close to that extra week and even at that date there is still a couple of day margin of error. Better they should date you earlier rather than later so I'd just go with it.

My ultrasound dating puts my babies due date exactly where I thought I ovulated (*8* days after DTD though) but they decided to stick with LMP dates instead, I'm not sure why, since I always ovulate a little late the Ultrasound dating is almost certainly the accurate one but in my case its only a difference of 3 or 4 days so I'm not going to fight about it. (besides I have a weird superstition that if the date is earlier maybe the baby will take the hint and be born a few days earlier, and thus further away from Christmas)
post #10 of 25
I've been thinking of making a thread about this too! So, I have no advice, but if you don't mind, here's my situation.

I thought I was seven-ish weeks, but they said the sonogram measured six weeks four days.

I'd montored my ovulation first by cervical fluid observation for a while and then also with those pee tests for the last two months before my BFP. However, I'm not entirely sure when I ovluated the actual month I concieved, because there was a discrepency. The day that cervical fluid observation indicated I ovulated, which also lined up both with what the test had said last month, and with what the cf observations had indicated over the past several months, I didn't get two equal lines on the test. However, I did take more than one that day, and the color of the test line changed in such a way (first darker then lighter? I can't even remember) that made me think I'd just missed the point where the lines were equal. But I kept taking the tests anyway, and two days later, two perfect equal lines. There was dancing on both days, and also the day before the first possible date.

Now, my observations suggested that I usually ovulated around day 16-17, and I know it's usually assumed to be 14 in a 28-day cycle. So the first day I could have ovulated was day 17, and the other one was 19. I pretty much felt like it couldn't even be possible, because there wouldn't even be time for implanting, but I suppose I don't know if my period would have been late (it never has, though, in 25 years). Could the issue be that the calculations are all based on the idea that I had to have ovulated on day 14?

Now, I don't really care about the due date, I just worry that something is wrong. I had spotting, which is why I had such an early sonogram. And then I had actual red spotting two days after the sonogram, so I went to the hospital and had another one. I asked if the heartbeat was good for almost seven weeks, and the doctor said was "GREAT!" very definately, but I don't know if it was just normal and she wanted to make me feel better, or if it might mean the baby is older than they thought.

They seemed very casual about the change, like it wasn't unusual or worrisome, but I wonder if they just assume I was wrong about my LMP. I did actually mean to ask the doctor this, but my last appointment was the day I had the red spotting, so I was too upset to remember all the questions I'd meant to ask.

Does it matter? Or is it just one of those things?
post #11 of 25
I think you should ask your physician these questions. It sucks that they are arbitrarily choosing your due dates without having a conversation with you.

Ideally the doctor should have a conversation that goes "Your ultrasound shows this date, which is accurate plus or minus x days at this stage. If ovulation/fertilization/implantation was delayed, then that means xxx. Your estimated due date based on this will be xxx."

It sucks that you're not getting the communication that you want/need. My midwife asked me "how did you date your pregancy? How sure are you of these date?. Would you like to consider having a dating ultrasound- these are the risks/benefits. Given the information you have given me, my "best" estimated due date is XX. Does that sound reasonable to you?"
post #12 of 25
Quote:
Originally Posted by mom2sol View Post
Personally I would fight your Ob on this. Due dates are more important than you may initially think- if you go past.
I agree, except for the fact that your due date (and that of the pp who had the same experience) was made a week LATER by the doctor's change. Do you really want to fight to have the earlier due date, and then if you go past be told you're not allowed to go over 42 weeks without being induced? Fine to note in your records that there are two possible due dates, but I'd say go with the latest possible one you can get. All it is is an estimate in any case - doesn't really matter what the due date is except when it comes to going past due and some doctors'/midwives' rules about that.
Honestly, you might be sure you're right, but I wouldn't worry about the change. Just look at it as giving you some extra breathing room.
post #13 of 25
Quote:
Originally Posted by Polgara1111 View Post
Well here's the thing.

On July 31 I had a pretty in depth ultrasound. And the tech said, "Oh your follicle is 22mm. Women ovulate when their follicles are between 19 and 24 mm so I'd say you're going to ovulate in the next 12 to 24 hours." That's when we did the dance, although truth be told, we were doing the dance every couple of days that whole rest of the week cuz we were on a lovely vacation with lots of time for dancing.

So I have assumed that I ovulated on August 1 or at the latest, August 2.

But this new due date puts my ovulation at August 7. Do you guys this it's possible that I really did ovulate a week later than the technician thought? My evidence is based on what she told me but she's not a doctor.

I got a positive pregnancy test on August 16, so that would be only 9 days after my supposed ovulation.

They determined due date with the ultrasound, the heavy duty one, not the one the nurse practitioner brought in. She said I was measuring at 6weeks when I thought I was at 7 weeks.

What do you guys think?
Polgara, based on the above, I think you should trust the dating ultrasound and your doc's calculations. It's very possible you ovulated later than you thought. Getting a positive pregnancy test after 9 days sounds about right to me. I got my first positive test at 10 days past ovulation, and I was testing everyday.

If you were absolutely 100% sure, without a reasonable doubt, of your conception date, I'd say go with your date and make your doctor change it. But given that you aren't 100%, the accuracy of DATING ultrasounds around 6 or 7 weeks (yes, I know at other times ultrasounds can be unreliable, but at 6-7 weeks they're pretty accurate at determining at EDD within a few days), I would go with the doc's EDD. Just my .02. Plus, her date is a WEEK later than yours. If she had calculated your EDD a week EARLIER than you thought, I might re-think this since I'd fear induction. But since that's not the case with you, and given all I said above, in this situation I'd trust the doc's EDD (and believe me, I'm usually pretty skeptical of OB's!!!!!!)
post #14 of 25
WildWmyn,

I would trust the sonogram. At 6-7 weeks, they're pretty accurate for dating purposes. I think it's possible you ovulated later than you thought. I have a 28 day cycle, and I typically ovulate around day 18.

Quote:
Originally Posted by Wildwomyn View Post
I've been thinking of making a thread about this too! So, I have no advice, but if you don't mind, here's my situation.

I thought I was seven-ish weeks, but they said the sonogram measured six weeks four days.

I'd montored my ovulation first by cervical fluid observation for a while and then also with those pee tests for the last two months before my BFP. However, I'm not entirely sure when I ovluated the actual month I concieved, because there was a discrepency. The day that cervical fluid observation indicated I ovulated, which also lined up both with what the test had said last month, and with what the cf observations had indicated over the past several months, I didn't get two equal lines on the test. However, I did take more than one that day, and the color of the test line changed in such a way (first darker then lighter? I can't even remember) that made me think I'd just missed the point where the lines were equal. But I kept taking the tests anyway, and two days later, two perfect equal lines. There was dancing on both days, and also the day before the first possible date.

Now, my observations suggested that I usually ovulated around day 16-17, and I know it's usually assumed to be 14 in a 28-day cycle. So the first day I could have ovulated was day 17, and the other one was 19. I pretty much felt like it couldn't even be possible, because there wouldn't even be time for implanting, but I suppose I don't know if my period would have been late (it never has, though, in 25 years). Could the issue be that the calculations are all based on the idea that I had to have ovulated on day 14?

Now, I don't really care about the due date, I just worry that something is wrong. I had spotting, which is why I had such an early sonogram. And then I had actual red spotting two days after the sonogram, so I went to the hospital and had another one. I asked if the heartbeat was good for almost seven weeks, and the doctor said was "GREAT!" very definately, but I don't know if it was just normal and she wanted to make me feel better, or if it might mean the baby is older than they thought.

They seemed very casual about the change, like it wasn't unusual or worrisome, but I wonder if they just assume I was wrong about my LMP. I did actually mean to ask the doctor this, but my last appointment was the day I had the red spotting, so I was too upset to remember all the questions I'd meant to ask.

Does it matter? Or is it just one of those things?
post #15 of 25
Thread Starter 
Okay that puts me at ease somewhat. I guess we had the ultrasound at the exact perfect time for dating. We'll see what the next one shows on Monday. i'm having a low progesterone issue so I guess my fear is that the baby is not developing and that's why they think I'm a week less pregnant than I thought I was. We did see the heart beat and all that, but this low prog thing is bothering me. I'm on suppositories and it hasn't gone up. now they added oral prog so on monday we'll see if it's helping.
post #16 of 25
Quote:
Originally Posted by acp View Post
Honestly, you might be sure you're right, but I wouldn't worry about the change. Just look at it as giving you some extra breathing room.
Yep, just what I was thinking. If it were me, I'd only make a fuss if they were changing it to an earlier due date, not a later one.
post #17 of 25
wow! I'm so glad I'm not alone in this. I had a u/s at 7w4d that showed I was 6w1d. They want me to come back in next week for another u/s. My dd was born at home with a lay mw, and I never saw a dr, had a u/s, etc. The whole expirience was laid back, low-tech and wonderful. The only reason I went to my dr this time was b/c I had a mc in jan. I really feel myself getting pulled into the whole fear cycle of the med system. The more tests you have, the more fearful you get. I mean, if the baby's not developing, it's not developing, right. Having a u/s wouldn't stop me from having a mc. After this next u/s, I' m calling my mw and not looking back.
post #18 of 25
Quote:
Originally Posted by guitarmama View Post
I really feel myself getting pulled into the whole fear cycle of the med system. The more tests you have, the more fearful you get.
I know... I keep weighing my decisions... do I REALLY want to do this first trimester screening? Am I going to be able to stop the cascade of interventions?? It sucks. :
post #19 of 25

Here's a question

So, do all babies develop at exactly the same rate? I mean are all 7 week babies the exact same size, or are they measured using some arbitrary standard?
post #20 of 25
I might be wrong, but I think in those early weeks they pretty much do all tend to grow at the same rate, be the same size, etc. That's why u/s dating is pretty accurate in the very early weeks, but less and less accurate as you get farther along, and not used much at all for dating after the first trimester.
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