identical or sororal
February 26, 2009 11:40 AM Subscribe
Fetusfilter: what are the statistical chances that two female fetuses, 15 weeks, diamniotic/dichorionic ("di-di") are identical?
posted by whatgorilla to Science & Nature (14 answers total) 1 user marked this as a favorite
So evidently our twin girls (15 weeks) are diamniotic-dichorionic (di-di), meaning they each have a placenta and sac to themselves. This seems to mean that the chance of identicals (versus fraternals) is 11% (33% twins are identical, 33% of those are "di-di" so 1/3x1/3=1/9 or 11%).
HOWEVER, since we now know they are both girls, does that somehow affect the odds? It would seem to raise it again, but I have no idea by how much or where it would go in the calculation. Any ideas?