Baby's size

mallyandryan · February 2017

Our baby has been measuring in the 75th percentile so I had an ultrasound today at 30 weeks. Now she's measuring in the 15th. Has anyone else noticed a decrease in the size of the baby? My son stayed pretty steady the whole time, but I feel like that's a pretty big drop. My doctor didn't seem too concerned. Just curious if anyone else has experienced it.

lovelongdog06 · February 2017

I put zero faith in third tri size estimates. I wouldn't be concerned.

smoochie041719 · February 2017

I agree, they can be super inaccurate. I wouldn't put any stock in these measurements.

pammasu0909 · February 2017

@mallyandryan I just saw this. It's possible that your baby had a growth spurt then slowed right down. Percentiles are crazy and continue to be crazy even after the baby is born

If the doctor isn't concerned then you definitely don't need to be!

catem07 · February 2017

I think doctors only get concerned if the baby is in the 10th percentile or below, probably in part due to the inaccuracy of those estimates. Even though it feels like 15 is so close to 10, I'd try not to be worried.

Magheeta · February 2017

I agree with PP's. My first started measuring small in the 10-11th percentile at the beginning of the third tri. They monitored his growth, but even then the doc wasn't super worked up about it. DS ended up being skronny when he was born, but still weighed like 6 lbs 11oz. He's always been on the small end since, and they basically told me that someone has to fit into those numbers statistically.

cafedisco · February 2017

I've not had much experience with inside babies' sizes but my daughter was in the low low percentiles as an infant. I was so reassured when my midwife would remind me that someone had to be those bottom 10%. As long as they are on the chart, it's OK.

lovelongdog06 · February 2017

My son was in the 2ND percentile for the first 6 months of his life. Lots of stressful pedi visits and one pedi switch later, he's 50% for weight and 95%+ for height. Sometimes they're just tiny and sometimes they just take time.

MrsBakes · February 2017

I've never heard of the measurements of the baby in utero once you are past the first tri screening etc. Maybe I'm misinterpreting this, but all my clinic does is tell you if the baby is measuring behind or ahead and if it's off by more than 10 days they may change the due date or of course do more tests if it's way off. But % growth chart like that isn't done. Also, as PPs said, i wouldn't trust the 3rd tri US to give you close measurements. MY OB never does them for that reason. And I can tell you from 3 people I know that the measurements they had done were way off. I wouldn't worry about it, especially since the doc isn't either

twistsandturnsto2 · February 2017

Like PP mentioned- there is a bit of a margin of error with these measurements. That being said, the 10th percentile and under is usually the benchmark for extra monitoring and concern. I'm at and/or just under that so I do have some first hand experience here. As long as everything else is looking good- trust your doc here. Babies grow at different rates in utero, just like on the outside, so one wonky scan may not be cause for alarm.

twistsandturnsto2 · February 2017

@MrsBakes a percentile chart is used for fetal growth and is used commonly to dx things like IUGR. From what I have experienced, u/s techs and docs don't mention it unless you fall under the 10th percentile- I never knew or heard DSs measurements as he was considered normal. This time they are all over me with numbers and extra monitoring because of our small baby.

Yes- weight and size estimates can me off in third tri- but they are actually measuring against a growth chart when they do scans.

schef070911 · February 2017

This is interesting because I was just talking to my OB today about getting a 36w ultrasound which she said was "up to me". She said that most women do them, but it didn't sound like she gets a lot of information out of it due to questionable measurements AND the possibility of labor/delivery decisions (e.g. deciding to induce or schedule a c/s with a projected large baby) being made off of said measurements.

She did say that she'll do one at 40 weeks (if no signs of labor) to make sure baby is doing okay and can continue to cook for a little longer. I'm dying to see LO again of course, but at this point I'm wondering if any information I get from another ultrasound would just complicate things if I don't really need it.

ETA: I'm also worried that if the ultrasound isn't medically necessary it'll somehow get billed as elective with insurance..... so there's that.

smallanimal · February 2017

Your baby didnt decrease!! still growing, just slower. If there is no other problem, I wouldn't worry. Some babies ar ebig, some are small. And they always, always grow in spurts!

MrsBakes · February 2017

This is interesting. I had my fair share of ultrasounds but all prior to 3rd tri and nothing was ever said about it so I was not aware of this at all... My ob told me yesterday that she'll do an US next visit when i'm 36w, but only to determine if he's head down. Like I said she never uses the US in third try for measurements. But I can see why this would be different if you are below a certain %. My ob touches the belly and assesses the size that way. It sounds crazy but she's dead on. When I was 39w with DD she touched my belly and said "Ah perfect 7lbs baby. DD was born 2 days later at 7.07lbs

Apparently she does magic LOL
I hope all is well and you don't have to worry too much, mama!

M&Max · March 2017

I have ultrasounds weekly now - they do measure every time and currently baby was in the 86th percentile (

) but they don't get concerned one way or another at my practice until there is a trend that is concerning. Babies in 3rd tri tend to have growth spurts so they could've just caught mine right after a big growth spurt or she could just be big... DS was always measured that he was going to be 9lbs - he was 7lbs 14oz so a little more than a lb off from the ultrasound measurements. I think in general they are just a guideline.

Dannylion24 · March 2017

I went for an unexpecteded growth scan on Monday (after belly was measuring a bit small) at 36 weeks and was so confused. The tech repeatedly mentioned how hard it is to get measurements when baby is this far along and didn't look at limbs or anything. She's like, "Well, what I can see looks fine, but it's not much." Her bedside manner was totally offputting anyways, but I found those comments to give me even more reason not to trust the size/weight measurements in the 3rd trimester.

MrsBakes · March 2017

Like i said before, I'm really confused about this. The %ile of baby in the womb has never been done or mentioned by my OB. But again, it could be because both my babies measured OK during 1st and 2nd try and my belly measures according to the week. So I'm absolutely not dismissing what other mommies here have to go through. I'm just trying to maybe ease your mind a bit based on what I've been told and what my friend has experienced:
My OB told me specifically that she never checks the baby's measurements by US because they are not reliable. And here is my friend's story: She was told (after the 3rd tri US to measure the baby) that she could never deliver her baby boy because he was around 11lbs. So they scheduled a c-section for the following week. Her boy was only 8lbs!!!
But like some PP also said, some people have small babies, some people have big babies. It doesn't mean there is anything wrong. So I hope nobody is being put through unnecessary stress. That's all i'm trying to say.

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