Two heartbeats in one amniotic sack is 99.9999999% identical twins.
Two heartbeats in one amniotic sack is 99.9999999% identical twins.
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Yes, I’m pretty sure that’s right. And for NORMAL identical twins, that’s not a problem. Cells from a pregnant woman can make their way through the placenta to an unborn child and cells from the unborn child make their way to the mother. That can sometimes/rarely make for future problems.
Identical twins (in the same sac as you point out) also can exchange these microchimeric cells through their shared placenta. Since they are identical twins with cells genetically different, that should never cause a problem. Since these half identical twins also share the same placenta they also “exchange” cells and thus become somewhat chimeric (have some cells with the slightly different genetic materiel from their half identical twin). I suspect that fetal exchange is how they ACTUALLY became chimeric instead of the convoluted attempt at explanation in the article.
The funny thing is that if the half identical twins had both been the same sex, they would have been far less likely to have the developmental problems they had/will have as a result of being different sexes (but having chimeric cells of a different sex).
That’s what my doc told me when my twins were born...same sac = identical...and they have spent every day since birth trying to look different...lol