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I have a friend that is pregnant with twins, but doesn't want to know the sex. Her doctor told her that he is positive they're not identical. I've read a lot about it, and identical twins do not always share the same sac, so how would he know that they're not identical? The only things I've found online say that in most cases, unless they're different sexes, DNA testing is necessary after birth to know for sure. My only guess is that they're different sexes. Any other ideas as to how he would know this?

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Asked by Anonymous at 5:10 AM on Jan. 7, 2009 in Babies (0-12 months)

Answers (2)
  • If the first US was done early enough he could have seen 2 yolks. Identical twins are one yolk therefore if he saw two yolks there is no way they could be identical. That is only possible with a very early US. I have identical twins and have researched thoroughly. Other than that you are right, she would have to wait until they are born and do a DNA test. The egg splitting early can cause seperate sacs and placenta.

    Answer by megmckn at 5:28 AM on Jan. 7, 2009

  • It could just be an opinion. My u/s tech told me my twins were fraternal. But the radiologists reprt reflected a di/mono multi gestational config, which means they are identical. Sometimes they just guess that seperate sacs and placentas are fraternal, maybe their is history of twins in her family, or her age could all be factors in his opinion.

    Answer by vsrillo at 7:27 AM on Jan. 7, 2009

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