Parents of twins and twins themselves are often confused about their zygosity. It is human nature to look for differences, hence twins and/or their parents may think they are not identical when they very well could be. The only way to really know for sure is via a DNA test.
TRA receives many queries from twins and their families interested in zygosity testing to determine whether a particular twin pair is identical (monozygotic or MZ) or non-identical (dizygotic or DZ). Quite often parents are misinformed during pregnancy and at birth regarding their children's zygosity - as prenatal scans displaying one or two placentas are not a reliable means of determining whether twins are identical or not.
Please read this article for more information.
The two most popular methods of acquiring the DNA samples needed to determine zygosity (i.e. whether twins are identical or non-identical) are by collecting blood or cheek cell samples.
You can learn more about TRA's special discounted testing offer HERE