Twin Test: DNA and Zygosity Testing

Most parents would like to know if their children are identical or fraternal twins. However, research tells us, that twin parents are sometimes misinformed during prenatal scans. Some identical twins are born with individual sets of membranes, which may lead to the mistaken assumption that the babies are fraternal. Some also believe that twins with separate placentas must be fraternal twins. But, in fact, around one third of identical twins have their own placenta.

One way to tell the difference is using a twin zygosity test, due to the fact that identical twins share almost identical genetic information, while fraternal twins share around half. The twin test is done by swabbing to gently remove cheek (buccal) cells and can be done from home. The procedure is noninvasive and works on twins of any age, newborns to adults. A twin test can be ordered online and is being offered by numerous private companies. However, if you are not up for paying for a DNA-test, you may find your answer by reading the below.

Answer these twin test questions

  • Do you have a boy and a girl? Then they are fraternal (but read this).
  • Do they have the same sex, AND do you know for sure that they shared a placenta? Then they are identical.
  • Do they have the same sex and individual placentas, or is there doubt whether the placentas have fused together? Then they can be either fraternal or identical. In this situation, choosing to be patient may do the trick. According to the Danish Twin Registry you should wait until the newborns are a bit older. If they look so much alike that friends and family can’t tell them apart, they’re likely to be identical. This method works in more than 95 percent of cases, they write on their website.



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