View Full Version : Changing due date?

06-18-2010, 06:25 PM
I had my 20 wk u/s today and the tech said she thinks my due date is wrong. This was my first u/s I never had one to determine due date. My original due date was just picked due to the date of my last period. The tech said it is up to the doctor to change my due date. My original was Oct 30th, tech said it should be Oct 19th and she was sure. Do doctors normally change due dates according to u/s?

06-18-2010, 06:31 PM
They can and do. Your doctor should discuss all the results of your u/s at your next appointment.


06-18-2010, 06:33 PM
Yes, the U/S is more reliable than the date of your last period.
Congratulations on 11 fewer days to go!

06-18-2010, 07:34 PM
They usually only change due dates based on first trimester ultrasounds. They are most accurate up to 10 or so weeks. They also correlate it with when you feel fetal movement, whether your fundus (top of uterus) is at your umbilicus @ 20 weeks & other milestones. I've had my due date changed 3 times (current pregnancy & with my 2 younger children). Always backwards. This time they moved my due date back by 9 days. Since we've started doing dating u/s, I am basically never overdue. I was 2 days overdue with my first, who was only dated by LMP. She also measured as small for gestational age. It's a pity I can't do a retroactive dating u/s, because I bet she was just fine.

06-18-2010, 08:07 PM
Ultrasounds are more accurate earlier on. But, they can change your date. Personally, if I knew my last period and knew that I had regular 28 day or so cycles, I would be arguing a 11 day change. I'd be worried about it being wrong and then pushed into everything too early.

06-18-2010, 09:47 PM
After the 1st trimester the accuracy of u/s goes down to about +/-14 days. I donnt know if iI would feel comfortable with a date change. And I would be very, very hesitant to evict baby before the onset of labor (no inductions or c-sections before 40 w, for sure, if all is well).


06-19-2010, 07:01 AM
Yes, our U/S tech suggested we were about a week further along than we thought. That's not much of a change, so I'm trying not to get my hopes up. I'm mentally sticking with the original date, and if he comes early, he comes early.

06-19-2010, 08:07 AM
My doc changed mine by 9 days because of an early ultrasound...and the 18 week ultrasound doctor agreed that it was correct.

06-19-2010, 01:27 PM
Mine was also moved up 6 days, even though I KNOW my conception date. I'm sticking with my date even though my OB says it's 6 days earlier.

06-19-2010, 01:39 PM
Mine was moved back both times based on a first trimester ultrasound. My doctor said they won't change it after the first trimester. Maybe some doctors do though. See what yours says.

Snow mom
06-19-2010, 02:08 PM
I would fight them moving your due date earlier. It determines when they will insist on scheduling an induction. It would suck to be induced because you are at 41 weeks when really you aren't even at 40 weeks yet. You can keep what the tech said in mind, but really dating at this stage isn't that accurate. IIRC, the dates on the ultrasound had a confidence interval and that confidence interval got wider on later ultrasounds.

ETA: I had an ultrasound at 7 weeks for dating (although I knew the date for my LMP and also what date DD was conceived.) The very early ultrasound suggested I was due 4 days after the date based on my LMP but the doctor said it wasn't enough of a difference to change my official due date. DD arrived 5 days late.

06-21-2010, 12:20 AM
at a 20-ish week us, it also matters how sure you are of your dates. if you are a regular person & sure when your last period was & your s.o. was gone the next week after you should have ovulated, don't go for a date change. if you gave the date your best guess but don't really have regular periods & you've been measuring larger, they'll take that into consideration.

but remember it's a 'due month' - since from 37-41 weeks is considered 'term' (with preference for 39-40 1/2), by the time you get to middle october it won't matter as much.


06-21-2010, 11:21 AM
I have heard ultrasounds are only reliable for due dates in the very beginning. My kid was 1/2 lb at 16 weeks which is pretty big, I think, for that date--but the one I had at 7 weeks was exactly in line with what I'd expect given that I used OPKs to get pregnant.

06-21-2010, 02:41 PM
My best friend had IVF to conceive her DS and was told around 22 weeks that he was measuring 2 weeks behind, which was technically impossible. Around 28 weeks, u/s showed 3 weeks behind, but a bit later (31), he showed closer to dates. They wound up taking him at 32 weeks for suspected intrauterine growth restriction, and at nearly 4 lbs, he wound up being exactly what he should have been at that gestation. I'm not saying it was an unwarranted C section, but the u/s was just SOOOO far off from what he really was that I wouldn't trust u/s to be TOO accurate in size/weight after 13 weeks. IMHO, I don't know how every single woman in the entire world can have babies be the exact same weight and CRL size at every single week or marker. That just defies the individual nature of baby humans being uniquely their own.

06-21-2010, 04:53 PM
PP reminded me of ds2's 20w u/s. He measured under 10% and I got all freaked out. But, within a few weeks he was above where he should be! He just obviously hadn't hit his growth spurt yet. He went from measuring really behind that week to being consistently 2-3 weeks ahead for all of the 3rd trimester (and born 9lb 9oz). I could have saved myself a lot of stress if I hadn't obsessed about just one u/s reading.