Fraternal vs. Identical

My OB has told us that our girls are fraternal b/c they each have their own sac. However, I've talked to several people who have told me that there are also identical twins who have seperate sacs and I guess I don't really understand the whole Mono/Di Di/Di yada yada stuff. I would assume ours are Di/Di. But then, I also read that the Olsen twins are fraternal?! That can't be right, can it? They look WAAAAY to similar.

Someone break this down for a hillbilly. Can identical twins each have their own placenta? I don't really care either way and am planning on the girls to not be identical, but this just boggles my mind.

TIA.

 

I found this all quite confusing too! My understanding is if there is one placenta (monochorionic) then the twins are identical. With dichorionic/diamniotic it can go either way - identical or fraternal - but the majority of di/di are fraternal. I wonder how your dr. is so sure...maybe there is more to this!

 

I'm glad you asked this, since I'm confused too! I assume we are having frat twins since I had IVF and had two embryos transferred. However, I guess it's a rare possibility that one of those embies didn't take and one split...though they both have separate sacs and placentas. Once we know the genders, that should help. If they're boy/girl than that solves the mystery!

 

70% of identical twins have a shared placenta (mono/di) and 30% have two placentas (di/di- just like fraternal twins.

The vast majority of di/di twins are fraternal but a small percentage are in fact identical twins. You will not be able to tell if di/di twins are identical unless you test their DNA after they are born.

 

Only way to say for sure while they are in utero, that twins with their own placentas and own sacs are fraternal is if one is a boy and one a girl. Once they are out - DNA testing.

Mono/Mono - shared placenta, shared sac
Mono/Di - Shared placenta, seperate sacs
Di/Di - separate placenta and sacs.

Depends on when the embryo splits as to what you end up with. If it splits in the first 3 days, they will have their own placentas. During day 3-8, they will share a placenta. Days 8-12 they likely will share a sac also. After day 12 is when you end up with conjoined twins.

You said yours have their own sac - do they share a placenta? If they do then they are likely identical...of course to add more confusion, to non identical placentas can fuse to look like one......

Yah.....a whole bunch of fun! LOL

 

I think they each have their own placenta. Being as they are both girls, I would assume that had they shared a placenta they wouldn't have been so "sure" about them being fraternal?

It's hard for me to tell. When she measured the Amniotic Fluid at my last U/S it said Quadrant 1,2,3,4 but It didn't appear that she was measuring two different placentas to ME, but what the heck do I know.

Is the "sac" the same thing as the placenta? And does the "divider" seperate the placentas? Is that how they tell?

 

It all depends on exactly when the embryo split. The sooner it split the less likely the twins will share anything. But having di/di twins does not mean they are fraternal for sure...it just makes it a little more likely. One surefire way to find out is if they have clearly different bloodtypes or eye color or hair color at birth. Identical twins can have different weights and heights, but they should have the same eye color and hair color. But then again...frat twins can share the same eye color and hair color, so just because they look the same doesn't mean they are identical either. I'm an identical twin, and my sister and I have some slight differences in our face shape and height. My neighbors have frat boys, who look totally identical except that one has blue eyes and the other has brown eyes.

 

Oh, regarding the placenta thing... it's quite possible that frat twins have placentas that are so close together they can be difficult to measure separately. The u/s tech was not positive that I had frat twins until I was far enough along to distinguish sex because their placentas were very close together. It was impossible, at that stage, to see if I had one or two placentas.

 

The sac is different from the placenta. The baby resides in the sac with amniotic fluid surrounding her. The baby's umbilical cord connects the baby to the placenta, which is outside the sac. The placenta is how the babies receive blood, oxygen, etc.

 

If you transferred on day 3, there is a small possibility that they are identical. If you transferred after day 3, and they are di di they must be fraternal. It would be too late for them to form their own sac and placenta!!

 

True - if they were 'sure' they are fraternal then they likely do have separate placentas. You likely would have been told more because if they DO share a placenta it opens a whole new can of worms in regards to their growth and other issues that can come up with monochorionic pregnancies. THe 'divider' they speak of is likely the membranes between the babies. In monochorionic pregnancies that membrane is super super thin. Its a bit thicker in dichorionics.

 

One more question to add to the whole pile here.....when can they tell, or rather see, the placenta on the u/s? We had an u/s at 6wks5d which is when we found out there were two and they just said "separate sacs". However, we have a scheduled ultrasound on Wednesday to measure and do the first trimester stuff. I'll be 12wks2d at that point. Will they be able to tell on the placenta then?

We're just really curious because my older sister has ID twin girls (they are 10 now) so it will be interesting to see what we wind up with.

 

They are di di twins if there were two separate black holes. And if your doc said that at that early of a stage, then they ARE di di twins. Did you seee two black holes with one baby in each? With mono di twins, there is only ONE black hole with two babies in it. What did yours look like?? Can you post a picture?

Were your sisers mono di or di di identicals?

Even if they are di di, there is still a chance that they are identical, albeit a small one. Keep us posted!!

 

They were definitely two black holes with a baby in each. I have no idea what my sister's were. It's been so long.

I think it's kind of cool though that both of us will be having twins and it was all nature for both sets. Neither one of us used any fertility drugs or IVF or anything like that. Not that there's anything wrong with those, but I just think it's a little cool.

 

My girls shared nothing. We were told fraternal as well but after they were born, there were waaaay too many things the 'same'. Dna came back identical.

The only way you will know is probably after they are born. And even then, if their head shapes are different, they faces may look different to you. You really have to look closer...at the eye shape, the nose shape, the hair line, the hair swirls, the ear swirls, the fingers and toes...if there is something shaped uniquely that they both have. Stuff like that.
Same sex, same blood type.
Even than though, dna is the only way you will know 100%.

 

I don't like it when the doctors tell the parents their babies are ID or Frat unless of course they know for sure because of mo/mo twins or boy/girl. A lot of the times it seems the doctor is either guessing or doesn't know what he/she is talking about. I'd say if your girls come out looking a lot alike and have the same blood type, get them DNA tested to know for sure.

 

Will they check their blood type when they are born? I can't remember if they did that with my son.

 

some hospitals do, some don't. The hospital where I had my first 3 did test blood type, but the place I had my last one at didn't...

 

The blood types weren't checked on our guys. If i had asked they may have, but we didn't.

 

I also have di/di twins that are Identical.

 

Others have said it better. Only way to know for sure is DNA testing unless it's boy/girl twins.

 

I am Rh- so they always test my babie/s blood type/s to see whether or not they need to give me another rhogam injection.

 

We assumed since the ultrasound showed di/di boys that they were automatically frat. Quite a surprise when the peri told us that they could be either iden or frat and we would be able to tell once the boys were born. If we aren't sure, then we can have the genetic test to confirm. It feels strange to have that up in the air.