how do you know for sure your twin babies are identical from looking at the sonogram?

Question

the doctor said they are identical for sure, 3 month sonogram

Answer 1

You really can't tell for SURE without a DNA test... while they may only see one placenta, it very well could be two fused together. Of course, even if they do have two seperate placentas, they still could be identical :-p With fraternal twins, you will always have seperate placentas, seperate sacs,etc. But with identical twins, it's all about when the egg splits... if the egg splits almost immediately after conception, they will also develop seperate placentas, seperate sacs, etc. The later it splits, the more they share. Most identical twins (about 70%) do share a placenta but are in seperate sacs (that's how mine were) which means the egg split somewhere between 4-8 days after conception. Some actually share a sac because it split even later than that... and on the extreme end of the spectrum, if the egg splits like 2 weeks after conception, is when you get conjoined twins...

So, in short (I know, too late :-p), looking at placentas, sacs, etc. is a very unscientific way of telling the zygosity of twins (whether they are fraternal or identical). DNA test is really the only way to know for sure... the only exception is if they develop a condition like TTTS (Twin-to-Twin Transfusion Syndrome) which is exclusive to identical twins (that's what happened with my girls).

Answer 2

Identicals, and only identicals, have a single placenta and a single membrane.

Answer 3

Hmmmm...that is weird, one can not know for sure till 6 to 8 months...But if he/she says so.

Good luck and congrats on being pregnant...:)

Answer 4

There is only one sac.