identical or fraternal in utero?

sweetsugarmama · December 2011

So I had an IUI and injections to get pregnant. First u/s at 5 weeks showed 1 sac, at 6 weeks showed 2 sacs. They are di/di from what I understand. The u/s tech at the time said they were fraternal.

Now I was reading google to try to understand the mono/di, di/di,etc thing and some say even if it is two sacs, two everything they could be identical.

I feel stupid for still not understanding this. Now that it's two boys I guess I wonder even more!

So can they be sure they're fraternal in utero? or do you need to wait and see?

flutepharm87 · December 2011

There are 2 ways to undeniably know in utero whether or no they're fraternal or identical. Mono/mono twins are always indentical (they're in the same sac) and boy/girl twins are always fraternal.

Other than that, if you have an early u/s that shows 1 placenta (mono/di), you usually have identical twins. Sometimes they end up being fraternal because the two placentas implanted close enough together that they fused. If you have di/di twins, you have a 1 in 9 chance of them being identical.

If you're questioning it, the only way to to know is wait until they're born and spring for a DNA test. Depending on which company you use, it can range from $100-$200 and it can take several weeks to get the results. But you'll have definitive proof. Or, you can PIP and ask our resident Peakay if they're ID or frat!

Missa_g · December 2011

My understanding is that di/di twins are almost always fraternal. There is a small chance that one fertilized egg split super early and each formed their own amniotic sac and placenta despite being identical. I hope someone will chime in and tell me if I'm right!

UsedToBeGoldie · December 2011

since you did IUI the chances of ID are very small... since IUI doesn't = more chances for an egg to split like IVF often does (b/c it can weaken the eggs).

my boys are fraternal from clomid/IUI - i knew i had 2 follies on my IUI day -so i never expected ID twins... and they came out with different blood types and are total opposites in looks (blonde/brunette, brown/blue, etc).

you can only assume they are fraternal - and when they are born if they are same blood type and look alike- then youc an do DNA testing to confirm.

mars724 · December 2011

they decided mine were identical because they are mo/di and it's appeared the whole time that they've been sharing a placenta.

I think it's probably more likely that they're fraternal if you had the IUI.

But, like someone else said, the only "for sure" is mono/mono are identical and boy/girl are fraternal.

tootlebug · December 2011

i mean logically, since you did injections im sure you had more than one mature follicle. they are probably fraternal. yes there is the major off chance that only one egg made it and that one egg split, but highly unlikely.

(and it's not because you did IUI. you could have had one mature follicle and still did IUI. IUI alone doesnt up your chances for multiples - it's the drugs you used in conjunction with it, which were injections, which im sure you produced more than one mature follicle),

Temp6313048411121614 · December 2011

After they're born ask the nurses what their blood types are. If they have different blood types there's no need for the test. One of my twins is A+ and the other is B+ so there was no way they could be ID.

sweetsugarmama · December 2011

thanks ladies! I'm def thinking fraternal, just google research got me confused. which is why I usually don't use it for medical stuff!

macchiatto · December 2011

Ditto flutepharm!

Missa_g:
My understanding is that di/di twins are almost always fraternal. There is a small chance that one fertilized egg split super early and each formed their own amniotic sac and placenta despite being identical. I hope someone will chime in and tell me if I'm right!

It's not that small of a chance. 1 in 3 sets of twins is ID, and 1 in 3 sets of ID twins is di/di. So that's why there's a 1 in 9 chance of di/di sets being ID.

We were told at 12w that my boys were di/di and the u/s tech told us what I just mentioned above. We found out they were both boys. At birth the nurse told us there was only one placenta, but it must have been two that fused. They look very different. (One blond, one brown hair, very different faces, etc.)

macchiatto · December 2011

Btw, OP, your daughter is beautiful!

natb22 · December 2011

Our girls were in seperate sacs (di/di) and ended up being ID!

chrissc34 · December 2011

My boys are di/di. Two sacs, two placentas. Baby B is weighing 5oz bigger than Baby A. I just assumed they were fraternal no matter what. Very interesting. Either way I love them to pieces already and they aren't even here.

Mrs. Alice · December 2011

Also if they are mo/di confirmed by first trimester or early u/s, it is like 99% certain they are identical. It becomes harder to distinguish between one placenta (mo/di or mo/mo) and a fused placenta (di/di) later on. Since you used fertility drugs and IUI and they are di/di, it's pretty safe to assume they are fraternal. The 1 in 9 chance of di/di being identical is likely based off of spontaneous twins.

tootlebug · December 2011

i thought with identical twins, di/di was still pretty common....the egg splits in two and then they travel off in their own little directions and form their own little sacs/placentas. i thought that this was the more common scenario with identical twins actually, as opposed to sharing the same sac....

Haven1 · December 2011

tootlebug:
i thought with identical twins, di/di was still pretty common....the egg splits in two and then they travel off in their own little directions and form their own little sacs/placentas. i thought that this was the more common scenario with identical twins actually, as opposed to sharing the same sac....

Nope. 1 in 9 di/di twins are identical. 9 in 9 mo/di twins are identical. (With a teeny chance of a fused placenta.)

The confusion comes with defining the word "sac". Amnio sac verses placenta sack. Depending on when the egg splits, yes, they may drift off and form their own placenta. That's the 1 in 9. Mo/di twins share a placenta sac, but most of the time they have their own amnio sac. Mo/mo twin share an amnio sac AND a placenta sac. It's very rare and very dangerous.

tootlebug · December 2011

Haven1:

tootlebug:
i thought with identical twins, di/di was still pretty common....the egg splits in two and then they travel off in their own little directions and form their own little sacs/placentas. i thought that this was the more common scenario with identical twins actually, as opposed to sharing the same sac....
Nope. 1 in 9 di/di twins are identical. 9 in 9 mo/di twins are identical. (With a teeny chance of a fused placenta.)
The confusion comes with defining the word "sac". Amnio sac verses placenta sack. Depending on when the egg splits, yes, they may drift off and form their own placenta. That's the 1 in 9. Mo/di twins share a placenta sac, but most of the time they have their own amnio sac. Mo/mo twin share an amnio sac AND a placenta sac. It's very rare and very dangerous.

that's where i was getting confused. i thought it was either separate everything or the mo/mo situation which i was knew was pretty rare but serious. so is there a slightly greater risk when it's mo/di or is it considered pretty much the same as di/di?

kiwi443 · December 2011

In response to the last question, there are greater risks with mo/di twins. There are some shared blood vessels, which can lead to Twin to Twin Transfusion Syndrome. One twin gets too much blood and the other doesn't get enough. It's very dangerous for both babies.

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