Could my Dr be wrong on the due date?

lcmilla · July 2012

I went in for my first u/s when I thought I was 9 weeks ... only to hear from the dr that I was only 6 weeks! Which means I would have gotten my first positive pregnancy test at exactly 7 days past conception. So there are a couple of reasons why I'm questioning whether my Dr.'s date is right.

1. I've never missed a period in my life.... I've always been extremely regular. It seems a odd that I'd skip a cycle, or even be 3 weeks off schedule right before getting pregnant

2. The ultrasound machine was brand new. It took them a little while to try figure out how to use it.

3. When I had my 2nd ultrasound at 10 weeks(their timing) I was measuring atleast a week ahead of the original u/s(she even commented that the baby looked more like 13 weeks developmentally even though she stuck with the original u/s dates).

I'm not sure if I'm just being stubborn because I don't like being wrong or if my gut is right and I'm actually a little further along ... Anyways, is there a possibility that they can get acurate measurements at my 20 week u/s?

MrsT1108 · July 2012

Unless you were temping and track when you actually ovulated, you cannot tell when you ovulated. Chances are you ovulated later than you thought you did. That being said you also do not know the exact date of conception. Just because you ovulated one day doesn't necessarily mean baby was conceived that very same day.

Babies don't all measure the same either. Some are smaller/bigger than others. Due dates also aren't exact, not many women actually have their babies on their due date.

The doc is most likely going by your LMP and under the assumption you ovulated on CD14 with a "regular" 28 day cycle.

ashdonne · July 2012

During early development, all fetuses grow at the same rate so your due date is probably pretty accurate. As you get further along babies do not grow at the same rate so its normal to have measurements that are off throughout your pregnancy.

drpayne · July 2012

MrsT1108:
Unless you were temping and track when you actually ovulated, you cannot tell when you ovulated. Chances are you ovulated later than you thought you did. That being said you also do not know the exact date of conception. Just because you ovulated one day doesn't necessarily mean baby was conceived that very same day.

Babies don't all measure the same either. Some are smaller/bigger than others. Due dates also aren't exact, not many women actually have their babies on their due date.
The doc is most likely going by your LMP and under the assumption you ovulated on CD14 with a "regular" 28 day cycle.

This. You really can't claim to be "regular" if you weren't charting. There is a lot more to a cycle than knowing how long it is. They can't change EDD at this point. The dating u/s is only accurate until about 8 weeks. After that, there is too much variation.

mAnYaSha · July 2012

I agree that unless you were charting, you do not know when you ovulated. That said, I personally would go by u/s measurements even if Dr does not change your due date on paper. DS#1 was born exactly on the date u/s way showing as due date, not what was on paper. Drs have their own rules about changing due dates, but I would say a week off should call for a change. For your personal self you can go with whatever date you feel is right. For Dr it is best if his due date is later than yours, so you would not be pushed into unnecessary induction.

schmucac · July 2012

Actually, a similar situation happened with me. When I had my 8-week ultrasound, the u/s tech said that there was no way I was 8 weeks and pushed me back to barely 6 weeks. I knew she was wrong because, although I didn't track my periods, I could tell when I was pregnant. I went to another doctor for what I believed was 10 weeks (to the other doctor, I would have just been getting to 8 weeks), and she clarified that I was in fact 10 weeks. I have stuck with this OB/GYN, and at my last ultrasound (last Friday) showed that we were right on track!

So mistakes can definitely happen, and if you're feeling completely unsure of what your doctors have said, maybe consider getting another opinion. Pray all goes well for you!

MinaE01 · July 2012

After your next u/s, talk to your doctor about the due date. I know they're very hesitant to change dates, but at least express your concern. 3 weeks is a big gap. The only bonus would be that if you wanted to avoid an induction, having a later due date would help out in that area.

I'm pretty convinced my doctor is off on my due date, too (I wasn't temping or charting but definitely know when I o'd- it was physically obvious to me). I'm not too worried because it'll give me a few extra days to avoid being induced.

Tiffany0416 · July 2012

It's a possibility. My husband and I thought our doctor was wrong and when we went in to find out the sex we also found out that we were right about how far along I was and the doctor was only off by like two weeks.

sbevmc09 · July 2012

In answer to your question, yes, it's possible that your doctor is wrong.

However, as others have pointed out, without charting, you don't really know when you conceived even if you typically have regular cycles based upon when you get your period. With that said, based on everything you've said the first U/S is going to be the best predictor of your EDD, but it's not 100%. What will work in your favor is you think you're further along than they think you are so it could help you at the end if they're going to be anxious to induce you based on EDD. I would talk it over with your provider next time. They probably won't change your EDD in your file, but I think it's a good thing to voice your concerns and let them know.

sesigs · July 2012

MrsT1108:
Unless you were temping and track when you actually ovulated, you cannot tell when you ovulated. Chances are you ovulated later than you thought you did. That being said you also do not know the exact date of conception. Just because you ovulated one day doesn't necessarily mean baby was conceived that very same day.

Babies don't all measure the same either. Some are smaller/bigger than others. Due dates also aren't exact, not many women actually have their babies on their due date.
The doc is most likely going by your LMP and under the assumption you ovulated on CD14 with a "regular" 28 day cycle.

This. Just because your cycles are always "regular" doesn't mean you always ovulate on CD 14. I would personally trust the dating on the first US. And growth changes after 8 weeks don't really mean much because babies grow at different rates the entire time.

beckpreg · July 2012

I'm in a similar boat but just dropped the issue since the Dr. and I only have a difference of a week. I, on the other hand knew by pain that I was ovulating and also took an ovulation kit which was positive. I wasnt temping but felt this was pretty conclusive. It was also day 13 after my period and when I normally ovulate.

Dr. says the baby is a week ahead. I just think he's a big one but oh well. Even yesterday she said he is now another day ahead. My only issue is that I dont want them to encourage me to schedule an induction b/c they THINK He is a week late when I really dont. But we will cross that bridge when we get there in December. Hopefully he will come on his own at a date and time that makes them happy.

HAFranklin · July 2012

My first u/s was off by 2 weeks. I went in when I believed I was 6 1/2 weeks. I had gotten a positive pg test almost 3 weeks prior. The u/s put me at 4 1/2 weeks. I knew it was wrong because 1) I probably wouldn't have tested positive when I did. and 2) We saw a heartbeat, and there isn't one yet at 4.5 weeks.

Based on my LMP, fundal height, and anatomy scan, my original date was correct according to my OB. He said that the fetus is so tiny that early on, and if the tech takes the measurements even a millimeter off, it can make the results off by weeks.

mest1215 · July 2012

due dates have nothing to do w/ your period, they are based upon conception. and as PP said, if you dont know when you ovulated, you dont really know how far along you are. Not all women ovulate on the 'by the book' 14day, i ovulate on my 21day, so my due date woulda been off by a week if i wasnt tracking my O days.

ta78 · July 2012

They could be wrong, but you also could have O'd late. It is hard to say.

You can talk to your Dr about your concern, but they are less likely to change the due date later on. Just keep in mind what you think your due date is, since your drs is 3 weeks later they won't push you for induction or anything. You will either have your baby earlier than they thought or later than you thought. Few babies are actually born on their due date.

MangomamaFL · July 2012

It happened to me. I had a doctor who was wrong on the due date.

Here a copy of an e-mail I sent about the topic: (I am too lazy to re-write the story)

"Actually my 3rd son measured five weeks older at the "20 weeks" scan. (The "20 weeks" ultrasound scan was done at 22 weeks since LMP). With that pregnancy I had quickening three week earlier that I had with my two previous pregnancies. The doctor 's office wanted to knock off five weeks my expected due date. I suggested that they should knock off only three weeks because of the early quickening. They weren't willing to change my due date to three weeks earlier rather than five. I left that doctor's office and found another health care provider who believed me. I requested a copy of the ultrasound report. It had an error range of +/- sixteens days. My son was born exactly sixteen days after the new expected due date (based on the ultrasound). This was three days shy than the expected due date I suggested. He wasn't induced."

With that said:

Your ultrasound was done early in the pregnancy. Earlier ultrasounds are more accurate than later ultrasounds:

Before 13 weeks: +/- seven days

14-20 weeks: +/- ten days

21-30 weeks: +/- fourteen days

31-42 weeks: +/- twenty-one days

Considering that your second ultrasound was done at ten weeks (based the first ultrasound) matches closer to the gestation you expected, your gut feeling could be correct. Let say if you didn't have the first ultrasound and your second was your first, they would likely have an EDD that matches to what you expected.

If your 20-weeks ultrasound measures to match to the second one done around "10 weeks", I think you should bring up the issue with them.

MiahT · July 2012

I went into my first u/s with due date of Oct 29th based on my last period, but the mid-wife told me I was almost two weeks behind that and pushed the due date to Nov 9th. The next week my OB did a u/s and told me to come back in two more weeks because she was pretty sure the first (really second) estimate was wrong by more than five days. Two weeks later I ended up with my third due date of Nov 3rd. Long story short, yes, sometimes the EDD can shift.

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