Identical and Fraternal Twins

Is it harder to detect Identical or fraternal twins in a ultrasound.

[pmperez]

Identical twins are in the same sac if Im not mistaken, and fraternal have their own.

[alaysha]

I would imagine it would be harder to detect identical since one could be hiding behind the other.

[heatherlynn22]

sometimes identical twins do have their own sacs. it just depends if the egg split within the first 12 days or not. that's why my ob is having problems determining if mine are identical or not. they share an aminiotic sac but two indvidual gestational sacs.