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Twins of significantly different sizes...

post #1 of 25
Thread Starter 
So, my DP is pregnant with twins. She is 31wks, 2days. We just had a scan done and the midwife was amused at the sizes. Baby A is 3lb 11oz, baby B is 4lb 6oz. I know the scans can be off by quite a bit (in fact, the first measurement showed baby B being 4lb, 13oz) but every scan so far has shown something similar.

The sono tech and the midwife both said that there is absolutely no indication of TTTS or any other problem, since both babies are pretty much growing on the curves they started on - they're just on rather different curves. But at this rate, if they stay on those curves and we make it to 38wks, we could have a 6.5lb son and an 8lb daughter. I'm weirdly freaked out by this. I kinda assumed they'd be similar sizes, at least at birth.

Has anyone else had two different sized twins? What did they look like at birth? They're both above average size for twins (Baby A is average sized for a singleton). Also, they are vertex-breech, does anyone know if the size of baby B is something we should be worried about for the birth? We didn't see the OB (who will attend the birth most likely) yet, but in the past he said that a vertex-breech presentation is "fine and normal" for vaginal delivery. He has lots of experience with both vaginal twin and breech singleton deliveries.

FWIW, DP & her dad are larger people, her sister and mom are smaller, so it's a distinct possibility we just have one baby taking after each side of the family. DP was a "BIG" baby (her mom couldn't remember weight) and SIL was a 6lber.
post #2 of 25
I have MZ girls so can't give my own experiences with weight differences -- but I did want to reassure you that since they are different sexes, they are DZ and therefore not at risk for TTTS. Also, they could be just different sizes (like any two siblings). So the US techs are right just to let each babe follow his/her own curve and not worry too much about comparing the weights to each other.

I think the only thing you might want to ask your care provider about it if there are any concerns about a vaginal birth with a much bigger Twin B. I think I recall my OB saying if Twin B was more than 25 percent bigger than Twin A, then that might rule out a vaginal birth? But that also might only related to them watching for TTTS and the 25 percent weight difference was a time to take action... I am sorry I can't remember (my girls are 5!) ... someone else will probably be able to help you out on that. But no worries in general about weight -- and congrats to her for growing such big babes!
post #3 of 25
Mine differed in weight, at birth, by about a pound and a half. Which was interesting, because my smaller twin (DD2, who was twin A and five pounds) looked more "mature" at birth, and her behavior was more organized, and she nursed better, than DS, who was almost 7 pounds.

They've consistently been different sizes, all along. I think that boys follow a different growth curve from girls, so with twins of opposite gender, this is probably a common pattern.

FWIW, though, mine were nearly exactly the same size, in utero, through most of my pregnancy. I think we first noticed a size discrepancy at about 32 or 33 weeks, and I was told that it was typical for opposite gender twins to start measuring differently.
post #4 of 25
Mine were both different sizes, with a di/di pregnancy. DD2 (baby A) was 6lb 5 oz and ds (baby B) was 6lb 11 oz. Not a huge difference there, but it continued to grow such that now at 10 months there is about a 2lb difference betweeen them. I will say that like Llyra, DD2 was more mature and nursed a lot better than her larger brother, DS. They were born because she broke my water. If DS had his way, I think they would have definately been born later.
post #5 of 25
mine came at 32wks, 3.9lbs and 4.7lbs. at 20mos, the bigger one at birth is now 5lbs bigger than his brother - he is just built completely differently. people often don't think that they are twins. they're a shoe size apart, too... which actually works out well, since the smaller guy gets the bigger guy's hand-me-downs

at birth, they both just looked like little babies... the difference didn't seem that huge then. as they got bigger and started to fill out, it became more apparent.
post #6 of 25
Thread Starter 
I think the funny thing about all this is that I'd heard of boy/girl twins growing a different rates, but usually it's a bigger boy and a smaller girl. Our girl is the one who is 10oz heavier than her brother! The midwife didn't express any reservations over their sizes in terms of the birth, but because it is a breech birth the OB will need to be there and we haven't seen him yet. We're also going to try a few things to see if we can get her to turn, though that is unlikely, according to the midwife. We see the OB next week.

Oh and the midwife did say that TTTS is not totally impossible for di/di twins, just far less likely. And so far, at least, the difference isn't quite 25%! I think I'm mostly just really startled by this since I assumed twins would be similar in size!
post #7 of 25
At 30 weeks my B/G twins were about 1lb apart in weight with dd being the heavier one. At birth she was 6lbs 4oz and ds was 5lbs 5oz. Ds quickly caught up though and probably surpassed dd by about 3 months. Now at almost 27 months ds is about 5lbs heavier than dd.
post #8 of 25
Our B/G twins were a pound apart, and were also vertex-breech. My OB said that if baby B was significantly larger than A, she would recommend a c/s. If they were similar weights, a vaginal delivery would be fine. If B is a lot bigger, then you have the usual dangers with a breech birth. It may vary from OB to OB as to how much a "significant" size difference is, but it's very possible that with a pound and a half it would become an issue. Now, my baby B was flipping around until the day I delivered them (ended up being an emergency c/s at 34 wks so presentation wasn't a factor in the end), so you never know if your B will end up vertex after all! Good luck to you and your partner.
post #9 of 25
Our di/di boys tracked a little apart in the growth scans, but not by a whole lot. The day we had them, we were told they were both around 6lbs. Well, BabyA was 6lb1oz, and BabyB came out at 4lb10oz!!! He was much littler. I don't trust those estimates at all!

BabyB struggled more, too. He was in the NICU for a few days because his breathing was "funny." He had reflux something awful. Little more wobbly, etc, etc.

Here at a year, they're about a half a pound different. That's a combo of A's curve slowing down just slightly and B's taking off.
post #10 of 25
My di/di twin boys had always been different sizes. I don't remember how much but at birth, A was 4 lbs 11 oz and B was 5 lbs 12 oz.
post #11 of 25
Originally Posted by TheGirls View Post
Oh and the midwife did say that TTTS is not totally impossible for di/di twins, just far less likely. And so far, at least, the difference isn't quite 25%! I think I'm mostly just really startled by this since I assumed twins would be similar in size!
With respect, it sounds like your midwife is uninformed or may be conflating something else with TTTS (don't worry, a lot of doctors and medical professionals do that too, it's not a strike against her).

*All* that Twin to Twin Transfusion Syndrome means is that the twins have an artery-to-vein connection to each other somewhere in the placenta. You can have vein to vein connections and artery to artery connections--those are still not TTTS. It is specific to the venal system of one twin connected to the arterial system of the other. Somewhere along the cell division process their circulatory systems did not fully separate, they are conjoined in a sense--just through the placenta instead of their bodies--and the circuit will be closed at birth. If they have separate placentas, that is *impossible* Sometimes separate placentas will fuse, sometimes there will be discordant access to nutrition because of placental placement or the size of the individual placentas (it could be possible for one to be crowded out).

But size discrepancy alone does not mean it's TTTS. That's a common and false assumption (and can lead to dangerous interventions and poor medical advice). It's certainly one of the first noticed markers for it. But it is possible to have hugely different sized MZ twins without TTTS (cord insertion problem in one, uneven division of the placenta) because that can happen due to a number of factors that have nothing to do with whether they have connected circulatory systems.

If one of your twins is not donating blood to the other, it is *not TTTS*.

It's very important that if you show complications in the growth of one twin that you do not allow uniformed folks to pigeonhole you into a TTTS diagnosis. Always get a second/third/fourth opinion, preferably from a peri who is *experienced* with TTTS. If someone is truly saying that TTTS is a size discrepancy only and that it's possible for two unconnected placentas to have a TTTS connection, then please make sure to get another opinion with all options/potential diagnoses explored or contact the TTTS Foundation.

Again, I cannot stress this enough--while size discrepancy is often the most noticable and first marker for TTTS, size discrepancy does not equal TTTS. Twins can have very little size discrepancy (esp. late onset). The opening of a vein-to-artery connection can even happen during birth. The significance of the syndrome is really dependant on the volume of that connection. It's not just size of the babies--but also amniotic fluid discrepancy, heart enlargement of the donor, irregular blood flow patterns. But even those individually could be caused by other factors. In reality, it's just a guess until the placenta is examined after birth and you get the findings.

I learned more than I ever wanted to know about TTTS because of my boys. Especially since we were always just below the threshold of the laser surgery intervention (when I was pregnant with them there was really only the Tampa center performing the surgery, and even then they had very very strict guidelines for who qualified). I spent 4 months in TTTS hell, in constant contact with many many families who were misdiagnosed (some of whom lost their children due to some really barbaric and unnecessary interventions for what didn't even turn out to be TTTS in the first place), still others who weren't diagnosed in time. So I take correct information about TTTS very very very seriously. A leap to TTTS diagnosis can be devastating, but so can the opposite.
post #12 of 25
Mine were 1lb 3oz apart at birth (38 weeks), and now at 4 years old my son weighs 10lbs more than my daughter (40 vs. 30). Their projected weights based on my last u/s before delivering were way off, my daughter was measured to be less than 5lbs and ended up at 5lbs 12oz and my son was 6lbs 15oz and measured over 7lbs.
post #13 of 25
My di/di twins were over 2lbs different at birth! Twin A, my boy, was 6lbs, 7oz, and measured average for a singleton at every scan. Given that they were 36weekers, I'm thinking he would have been HUGE by term! Twin B, my girl, was a peanut at 4lbs, 4oz. She surprised us. U/S estimates had her at about 5.5lbs--we had no clue she was so tinesy. Her cord and placenta were both about half the size of her brother's, so my OB thinks she just didn't pick as good of a spot to attach, grow, etc. She did a 10 day stint in NICU, but was perfectly healthy other than being small (maintaining temp was her main problem). Her brother was discharged with me. At 2.5, they're both healthy, average sized, and BUSY!

oh, and mine were vertex/breech, too, but given that A was my bigger, I had a vag birth. Baby B was born breech, but it was no biggie.
post #14 of 25
My twins (fraternal) were 4lb 0.3oz and 5lbs 8oz at birth (they came early). Both were in the 90/55th percentile for their gestational age and were just fine (other than some normal complications from being born early) at birth, and still at 3.5. The one who was 4lbs quickly caught up and I think within months, really, started to weigh more than the other, and has been consistently a pound or so more ever since.
post #15 of 25
my dp is a twin and he was born 5lbs 4 oz and his sister was 8lbs 6 oz. i know they were a c-section so im assuming there were issues but they were taken out at 38 wks.
even now hes a skinny guy and shes a big girl.
post #16 of 25
LOL an OB from my OB practice tried to tell me and my husband my b/g twins could have TTTS. And then justify it when I questioned him. (when I questioned him about continuing growth scans far into 3rd trimester)

Poor guy was just recently back off a LOA for chemo. So I cut him some slack but... Reading this made me think of that.
post #17 of 25
And, back on topic (sorry for the TTTS detour, but even after 7 years that is still close to my heart!). My boys are MZ and one was 6 lbs, one was 4 lbs at birth. They have stayed about 30 percent different in height and weight since (except for the first 6 months, my recipient/larger twin was way way way way roly poly because he was receiving a lot of rich milk that I was producing for his brother! Once they both started moving around more that wasn't quite so noticeable!).

I am told that they may even out once the puberty hormones kick in (just a few more years) and they start growing to their adult heights. I suppose that makes sense from a genetics point of view.
post #18 of 25
Thread Starter 
Oh and DP reminded me that the TTTS comment was made by the ultrasound tech, not the midwife, and the midwife we saw that visit is the "prenatal only" midwife anyhow, not a potential birth attendant. The OB at least is very experienced in vaginal singleton breech so we're hoping that he'll be ok with however they end up, lol. Though DP had an appointment today andd the midwife (the one who could attend the birth) strongly suspects they've moved again. Though she thinks girl may still be breech and boy may have gone transverse, which is hardly helpful.

However, she also said that they still have LOTS of room to move in there so she isn't making any assumptions about positioning yet. She also mentioned that she has done a version of twin B after the birth of twin A before. She is definitely still assuming we're doing this vaginally. (Which makes sense since this practice has to send us to a different practice to get a c-section if we end up needing one - they don't do sections)
post #19 of 25
At birth at 36 weeks, my MZ guys were 6lbs 7oz and 4lbs 14oz. "A" still has a few lbs on "B" even now at 7yrs old (and they're the same height).
post #20 of 25
My girl/boy twin sibs were 5lb12oz and 6lb14oz at birth at 36 weeks.

Now my brother tops six feet and weighs probably 300 lbs and my sis is 5'3" and weighs maybe 140? Okay, 20 years can do a lot!

My best friend's first b/g twins (yes, she has two, but I think the second set were pretty close in size) were also something like 5lb6oz and 4lb10oz at birth at 37 weeks. Her daughter was larger, and still is larger now that they're 6 or 7 or so.
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