5 day age difference in twins?

politelypink

I'm pregnant with boy/girl twins. Up until this past ultrasound, they were measuring 1 day apart. Yesterdays ultrasound showed that they are now measuring 5 days apart. Not sure if this is something I should be concerned about yet or not?

macchiatto

It's not really an "age difference"; when drs say that a baby is measuring, say, "15w6d," that just means they are the average size of a baby at 15w6d. A baby can be a bit bigger or smaller than that and still be within the normal range. I wouldn't be concerned yet at this point. There were appointments when my boys measured about a week apart, but at birth they were only 3 oz and 1/4" different.

Mrs. Alice

I concur with macchiatto.  I think it usually becomes a cause of concern when there is a 20% or more difference in their size.

dulcinea03

I agree with the PP. Especially after the 1st trimester, ultrasound measurements are not an exact science, and you're dealing with the laws of averages, so an 'average' baby measures X amount at Xweeks X days. 

As with singletons, twins can have a huge variation in weight. That's how you get some singletons that weigh 6lbs at full term, and others that are 10lbs+. While you don't usually see that significant of a difference in twins, a few oz-2lbs seem to be pretty common. What your Dr will look for is TTTS, if you're known to have mo-mo or mo-di twins, which can lead to serious complications. They also look to make sure both babies are growing and that their fluid levels and cord blood activities are normal.

Kit weighed right at a pound more than Jules when she was born, and has maintained that lb on her ever since. Others have had their smaller twin overtake their larger birth twin for weight as they grew up. You have to remember that while they're twins, they are still 2 unique babies with 2 unique growth curves, especially if they're fraternal twins. 

UsedToBeGoldie

if the docs aren't worried- then you don't need to be.

My twins were 2lbs apart at birth - and nobody was ever concerned at all of my many growth scans - b/c they always fell within the normal range - some babies are just bigger than others.  My boys are now 10lbs apart... so it's obvious, that's just how they were supposed to be- nothing went wrong while they were in my belly

macchiatto

Mrs. Alice:

I concur with macchiatto.  I think it usually becomes a cause of concern when there is a 20% or more difference in their size.

And this is true, too. If it's 20% or more difference you will usually get more monitoring to try to figure out the cause. 

klr210

ha ha ha.. I'm glad I opened the post..

I read the headline and was shaking my head thinking 5 day age difference was referring to another wacky comment or something.. lol.

my girls have always measured slightly different for average gestational age. my docs always said they were both great and they were happy they were both always bigger than the 10th percentile. also, baby a was ALWAYs the peanut measuring smaller than baby b. but unexpectedly at from 31 to 35 weeks, baby a had greater gains and is now larger, so i think a whole range of things is pretty normal and i wouldn't worry, especially so early when your talking about small weights meaning a big difference in avg gestational size.

politelypink

Thanks so much for the reassurance!! When my MIL was reading the ultrasound report she got me all freaked out. Can't wait to see the doc again in a couple weeks!

MaybeMore

But then there's this:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1626817/pdf/archdisch00782-0041.pdf

 

Sorry.  :-)  The idea made me curious.

macchiatto

MaybeMore:

But then there's this:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1626817/pdf/archdisch00782-0041.pdf

 

Sorry.  :-)  The idea made me curious.

Yeah, I know this has come up a few times on this board. Babies measuring slightly differently is very common, and makes sense since babies grow at different rates. It's very rare that you would actually know if multiples' age of conception truly is different, so it makes more sense to assume they were conceived at the same time and just growing at slightly different rates. Like Goldie mentioned with her twins having a very significant size difference; they just have different genes at play, and even identicals (who were obviously conceived at the same time ) can have significant size differences.