Mothering Forum banner

Size differences in MZ twins at birth and later

1141 Views 10 Replies 7 Participants Last post by  mamadawg
HI everyone,

Some recent posts about TTTS got me thinking. My mono/di girls were watched closely for TTTS and one was always bigger than the other, but it never passed over that magic point (20 percent difference?) where any action was required and they never called anything TTTS. K weighed 11 ounces more than O at birth (5.7 and 6.2) and to this day is always between a half and a whole pound heavier.

So is this weight difference (both at birth and still) just because she had a better position in the placenta? She started out as Twin B but at about 24 weeks moved vertex and stayed there, stretched out, while her sis was crammed in a breech position under my ribs for the last 13 weeks (ugh). Or perhaps when the zygote spilt, was K's somehow bigger/stronger or something?

Of course this is a completely frivilous question -- they are here and healthy and fine (more than fine!) at 21 months. But I always wondered if it wasn't TTTS, why the fairly substantial difference in weight? Will K likely always be a little bigger?

Thanks in advance for any thoughts you have! And congrats to all the new pregnant MOMs!
1 - 11 of 11 Posts
When my boys were born Byron was 7lb15oz and Miles was 8lb 2oz. Miles fattened up faster and got almost 1lb heavier than Byron but once they started solids (9-10 months) Byron started passing up Miles. Miles was way more into solids and not as into bfing and Byron still pretty much only nursed so I guess that made Byron gain weight faster. Now at 18 months Byron is 28lb 8oz and Miles is 27lb.
nak

i don't have twins, but i am one. i was 3lbs 8oz and J was 4 lbs 12 oz. she was also about an inch longer. we were 41 weekers, healthy, no ttts. now at nearly 30 she's still about 1/2 inch taller and usually weighs a bit more than i do. my dad used to joke that she just got 3/4 off the egg


i've always been curious as to the size difference myself.
See less See more
I think that there are a few possible reasons. If the umbilical cord was in a worse place (out toward the edge) then she may have had less blood available to her, but not nessisarily that her sister was getting some of her share. The other thing that comes to mind is that this sort of twin is called monozygotic because they aren't identical. Twins are often slightly differant in metabolism, in height and even in coloring. One may have a birth mark that the other doesn't have. KWIM? Their split may have caused certain traits to come out in one and not the other. It has even happened that MZ twins have been differant genders, but this is of course incredibly rare. If they are both growing then I wouldn't worry about whether one is a little bigger. If they didn't say they have TTTS they they probally didn't.
TTTS is not about weight differences or size differences (though obviously, those are "markers" because they are the effects of one twin donating blood to the other).

Unless your kiddos had vein-artery connections in the placenta, they did not have TTTS (which is formally diagnosed by certain bloodflow patterns detectable in US or upon examination of the placenta--size differences can tip off a doc to then take a look at the bloodflow pattern, but they do not diagnose TTTS). They *could* however, have had unequal shares of the placenta (a 55/44 split, say, or even higher, though it's believe that a baby MUST have at least 25-30 percent of the placenta to survive). It is possible to have one MZ twin have IUGR and the other one not, due to placental issues.

TTTS is a placental issue, but a very specific one. If you were being watched for it, and if they took your placenta to the lab for analysis/inspection, then the information should be in your file. Otherwise, it's probably safer to assume that the size difference probably is due to placental share independent of TTTS.

If you're curious, ask to see your file. Most doctors do at least a surface exam of the placenta, and will note where the cords are placed, ect. Probably your smaller twin had her cord placed in a slightly off spot, which would account for her accessing a smaller amount of the placenta. But TTTS is something very specific and different. Not saying your twins couldn't have had it, but less than a lb difference at birth is pretty mild for TTTS babies.
See less See more
2
Quote:

Originally Posted by Tigerchild View Post

TTTS is a placental issue, but a very specific one. If you were being watched for it, and if they took your placenta to the lab for analysis/inspection, then the information should be in your file. Otherwise, it's probably safer to assume that the size difference probably is due to placental share independent of TTTS.

This is just the kind of information I was looking for. Thank you for your post


They did look at the placenta in the lab and confirmed the mono/di and my doc never mentioned anything about TTTS, so I figured the weight difference was just part of who they were. But I will ask about where their cords were positioned -- that would be interesting to know.

I'll be curious to see if the weight difference continues throughout their lives. Ah, one of the many joys of twins -- watching to see who they become and what their "twinness" means. Thanks again!
See less See more
I should have added that my twins did not have ttts, they are mz but each has their own placenta.
2
Quote:

Originally Posted by LoisLane View Post
I'll be curious to see if the weight difference continues throughout their lives. Ah, one of the many joys of twins -- watching to see who they become and what their "twinness" means. Thanks again!

My boys were almost 2 lbs apart at birth, and about 2 inches different in length. They've stayed 2 lbs apart (though the bigger they get, the less it's noticable...it's not really apparent now unless you pick them up). Dylan is only about 1 inch shorter now.

My boys looked VERY different at birth. Because of the weight differences and some IUGR from both cord placement and TTTS, Dylan *looked* like a preemie. Tom didn't at all! My body made extra rich preemie milk for a long time for Dylan, and Tom really porked up on it (it was pretty funny). Now they look so much alike in photos (they have very different facial expressions, and personalities, so once people get to know them they can tell them apart easily) that sometimes I have to write down who was wearing what or ask them to identify themselves.

I will see if I can dig up some photos of the progression if people want, and post it in an edit. But don't worry if your babies don't look a lot alike. There are MZ twins that look very different, but chances are even if they don't look alike now they'll "grow into" it. I think you get the most comments about 'looking alike' when they're babies though, because to some people (myself included, unfortunately) most babies look more alike than different.
See less See more
I'm with TigerChild, my twins looked completely different at birth due to the TTTS. My recipient was pretty big for a 34w (5.10) and he was bright red from all the extra blood. My donor was way smaller (3.10) and he was pale and looked like a wrinkly old man.

Fast forward 4+ years, and the bigger one is about an inch taller and a few lbs heavier. I think that for "identical" twins, they're very easy to tell apart. Also, one wears Crocs all the time, and one only wears tennis shoes.

Strangely, in my opinion, they each have about 10 cowlicks in completely different places, so their hair grows a little differently. Dh cropped their hair really short a few weeks ago and as its growing out you can see the differences.
4
Quote:

Originally Posted by YumaDoula View Post
I'm with TigerChild, my twins looked completely different at birth due to the TTTS. My recipient was pretty big for a 34w (5.10) and he was bright red from all the extra blood. My donor was way smaller (3.10) and he was pale and looked like a wrinkly old man.
Would you believe in our case the colors were reversed? It totally freaked out the doctor. I don't know why Dylan (our donor) was so colorful at birth (later he just turned yellowish/orangish red from jaundice). The pics we have of them at a week old it's REALLY noticeable.

Of course, we found out later (within a day of bringing them home) that Tom was just pale because he'd picked up a staph infection in the hopsital and it had gotten into his bones.


But D was all wrinkly and little old man-like!
I'd totally forgotten about thinking that.
See less See more
2
Quote:

Originally Posted by LoisLane View Post
They did look at the placenta in the lab and confirmed the mono/di and my doc never mentioned anything about TTTS, so I figured the weight difference was just part of who they were. But I will ask about where their cords were positioned -- that would be interesting to know.

I'll be curious to see if the weight difference continues throughout their lives. Ah, one of the many joys of twins -- watching to see who they become and what their "twinness" means. Thanks again!
This is our case as well. My girls were monochorionic/diamniotic and I was monitored closely too. Baby #1 (she was Baby B, but was born first) was 4 lbs., 3.8 oz. Baby #2 as 4 lbs., 12.4 oz. They were born at 32 weeks, 6 days. The size difference wasn't significant, but Baby 1, the smaller baby, was very pale for a long time as an infant. I always wondered if a little bit of TTTS did occur and they just didn't note it.


They're 3.5 now and they weigh the exact same most of the time, but one is about 1/2 inch taller than the other. Funnily enough, it's the smaller baby who is taller. Up until about 6 months ago, the larger baby was always a pound more than her sister, but her sis has caught up with her in the weight department. It will be interesting to see how they grow as they get older.
See less See more
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top