Ultrasound at 38 weeks to determine size and position of baby

apichie · April 2016

Hi everyone, this is my second pregnancy and my 1st was 9lbs but I never had an ultrasound to determine size. This time around my midwife wanted me to get one because she wasn't sure if baby was head down and she also wanted to see size because my last delivery was hard on me. My question is how accurate are they at guessing size? Just wondering if anyone else had them in a previous pregnancy and how accurate it was. I went for it this morning and thankfully he is head down and he's measuring 6lbs 9ounces I have a week and 5 days left till due date

kporter18 · April 2016

I believe ultrasound size estimates can be off +/-2Ibs

kbrands7 · April 2016

While u/s are extremely accurate at pinpointing position, they're not wonderful at estimating weight. I've heard that generally the estimates are +/- 12oz. An u/s I had with DS estimated a birth weight of close to 9lbs. Had I gone into 41 weeks, maybe that would have been close, but he was born at 39+1 at 7lb5oz. This time around, they only assessed position at my third trimester u/s.

apichie · April 2016

Thanks girls

I figured that they could be off by a lot. My feeling is this baby will still be a big boy like my 1st lol I'll just have to wait and see. I'm so happy that he is head down and ready to go because my son was delivered semi transverse. I don't want to go through that again if at all possible.

finnybooboo · April 2016

I didn't have any late term ultrasounds for my last pregnancy either, with the exception of a quick check while in labor for position. So we were very surprised at her size of 10lbs at 40w2d. We just went on Friday for my 36 week appt and they said they'd estimate a +/- a lb. He was approx 6lbs 13oz at that appt, so they're estimating somewhere between 8-9lbs. She did say several times that because his head was so low, the measurements could be slightly off. If I wasn't having a RCS, they may have done another check for size leading up to my DD, but size doesn't really matter as much when you're not trying to push them out

apichie · April 2016

Yes, I think that's her concern if I should deliver naturally again or not. I go see her on Wednesday and I think because this baby is in position then she will say it's ok to go naturally. That's my hope anyways.

codeeye · April 2016

I'm going to request an ultrasound for size/position at my appointment on Wednesday. Last week the doctor told me my boy was "rather large" and to be prepared for the chance of an emergency c-section just in case. If I do need a c-section I would like to be awake for it (not something they do in emergencies unless you have an epi, which I don't want if I'm delivering vaginally) I wish he wouldn't have said something about his size. I would have much rather been surprised than to have approx 2.5 weeks to worry about it!

Nicbert1214 · April 2016

My doctor is sending me for one of these u/s as well next week. I'm not sure if it's routine for him to send patients, I think he is sending me because I gained a little over 50 pounds throughout my pregnancy. I have heard some measurements be off by up to 3 pounds though- so it kind of makes me wonder. My doctor has been adamant about the fact that they only perform cs if the baby is 10 pounds or over- what if they estimate him to be 10 pounds, they do a cs and he is only 7 or 8? Has anyone had this happen to them?

proudparent2b · April 2016

@Nicbert1214 I was estimated to be 12-14 pounds at birth, but was less than 8 1/2.

wamam027 · April 2016

My ob is sending me for one on 4/26. I was expecting this, my original due date of 5/6 was changed to 5/20 by my dating US done in CA with my old ob. Once DH and I got to VA in December, my new ob just went with the due date of 5/20 even though I've known there's little to no possible way of my due date being 5/20. They were measuring me Friday at my appt and that mixed with all of my false labor made them a little confused, so we go in to see how big baby is and check positioning (even though he or she has been head down for almost 2 months). I'm expecting them to tell me the baby is big for where I fall gestation wise simply because of that two week difference so I'm not too worried.

sapphirerose915 · April 2016

my doc is sending me for a US on the 28th to re-determine size and possibly estimate a new due date.
we have already done this twice because baby is so big. He just wants to make sure that baby and i are both ok and safe. I literally feel like my body is breaking tho so I'm not sure how much longer we can go!!!

katiebug1981 · April 2016

With my first they estimated her to be 11lbs 6oz and she ended up being 10lbs 5oz. At the beginning of April they estimated this one to be 6lbs 12oz already. I will have another growth ultrasound 5/6 and a csection on 5/10. My OB is sure he will be bigger than his sister but I'm hoping not too much larger

kp90 · April 2016

Should I be concerned that I haven't had an US since 20 some weeks and that was an elective 3D that we did on our own outside of my OBs clinic and my doctor said I won't have one from here on out. I would like to know she is still growing and developing the way she should be and also for them to tell me an estimate on size/position. I am a FTM and I guess from reading things on this app it has always made me feel my doctor is doing the bare minimum.. if anything! I feel I'm the one prompting everything. Idk. Maybe it's just me being a paranoid first timer but no one in the clinic even mentioned anything about the TDAP injection. Am I being a worry wart?

wamam027 · April 2016

@kp90 growth scans are typically not protocol unless they see something that requires taking a further look at the baby via ultrasound (fundal measurement is off, high risk pregnancy, etc). I wouldn't be having an additional US (my last was at 20 weeks for anatomy scan) if it hadn't been for me measuring ahead thus causing my ob to question my due date which I expected. I would not feel concerned in the least bit if my last US was at 20 weeks, simply means your dr hasn't seen anything that would imply needing a closer look at baby.

TinaTho · April 2016

@kp90 for the TDAP I would suggest just asking them for it. I think my office was a little lax on it too, but I asked for it last visit and got it immediately. Sonograms are usually if they are concerned about size, health of the baby... So unless you have concerns, I wouldn't worry about that too much. Of course this is coming from someone who has had likely more than 12 sonograms at this point. Best to always be your own advocate.

proudparent2b · April 2016

Seconding TinaTho - if you're not getting a bunch of extra testing, it's because you don't need it- everything is going well. That's a great situation to be in @kp90

kp90 · April 2016

Thanks ladies

Nicbert1214 · April 2016

@proudparent2b wow talk about being completely off! Geez!

barbieq101 · April 2016

I had an u/s today and baby turned from optimal position to transverse WHILE we were watching her on the ultrasound!! But now i swear i feel fingers way down in my pelvis where they should be. Anyone else have experience with a baby turning this frequently at 36 weeks? I'm not even sure what to google to see if this is normal.

BebeOnBoard · April 2016

Lurking from April. I just posted this, this morning:

i I had a growth ultrasound yesterday and they estimated 7 lb 13 oz.

i delivered 7 hours later and he was 9 lb 4 oz.

big difference.

Bellodomani · April 2016

barbieq101 said:

I had an u/s today and baby turned from optimal position to transverse WHILE we were watching her on the ultrasound!! But now i swear i feel fingers way down in my pelvis where they should be. Anyone else have experience with a baby turning this frequently at 36 weeks? I'm not even sure what to google to see if this is normal.

I never experienced it with my first, but this baby has been changing position multiple times a day and I'm 36 weeks. I'm having an U/S today to check position because she happened to be transverse during my appt last week but I swear she's just gonna keep doing flips until
it's go time. My midwife is comfortable with trying to flip her while I'm in labor/ delivering a breech baby if necessary though, so I'm operating on the assumption that I will still have a vaginal delivery.

apichie · April 2016

So I got a call back from my midwife saying his head measurement was off after the initial scan on Monday so she sent me for a second scan today to make sure it was an error because his head was so low, which makes it hard to get a good reading. For some reason the hospital here won't take the same scan over so I had to drive 35mins away to get it. Well my initial scan she estimated size at 6lbs 9ounces and today I got an amazing tech who is actually a teacher for students to become ultrasound techs and she was able to get a very good reading and told me the head size was perfect and not to worry. She also estimated his weight at 7pbs 8 ounces. So I'm more confident in her reading then the original tech. It goes to show you how far they can be off. The scans were only 2 days apart.

vinerie · April 2016

@kp90 That extra stuff is for high risk. I also only have had the 20W a/s.

Nicbert1214 · April 2016

I had the scan for growth today- she said 7lbs. 11oz. give or take 1/2 pound. After reading everyone's comments here- I am thinking it's give or take 2 pounds lol. They gave me a picture- he was gnawing on his arm- my boobs are in trouble

concreteayngel · April 2016

I only had a growth scan at 36 weeks because they were concerned about a somewhat low lying placenta at my a/s and wanted to follow up. It also seems like most of the time, they OVERestimate the weight instead of underestimating.

diabeticmom · April 2016

Just had my high risk u/s and the perinatologist confirmed that they can be off by 20%.

gardenandread · April 2016

I just had a growth u/s on Monday because I have GD, and they estimated baby was measuring approx 7lbs at a little over 36 weeks. My technician was also a teacher though and said that the farther you get into your pregnancy the harder it is to get accurate measurements, and measurements tend to be over estimated rather than under.

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