Are My Twins Identical or Fraternal?

Image of Identical or fraternal twins

Twin Zygosity

If you are pregnant with multiples, you will soon face unique joys and challenges that may not accompany the single birth experience. With twins, a common question parents have is whether the twins are identical or fraternal.

DNA Diagnostics Center offers a twin zygosity DNA test that definitively determines whether twins are identical or fraternal. A twin zygosity DNA test is a simple procedure performed sometime after the babies are born.

Some parents choose to start testing right away, while others prefer to wait to initiate testing until the twins’ features emerge later in life.

When twins are born, the physician is usually able to identify whether twins are identical or fraternal by examining the placenta; identical twins generally share a placenta, while fraternal twins are usually in two separate placentas.

However, for confirmation, a twin zygosity DNA test compares the twins’ DNA profiles to confirm whether they match. An exact match proves that the twins are identical.

The test consists of a painless buccal (cheek) swab collected from each twin. The swabs are shipped to DNA Diagnostics Center’s fully accredited laboratory where the DNA from the samples is extracted, analyzed, and compared.

Like all DNA tests performed by DNA Diagnostics Center, each sample is analyzed twice to ensure 100 percent accuracy.

Reasons To Consider a Twin Zygosity DNA Test Include:

  • Records from birth may be lost or inaccurate.
  • The twins’ placentas may have been discarded or damaged before twin zygosity was determined, especially in the event of an emergency or health-threatening birth experience.
  • Different physical traits may emerge as the twins grow, casting doubt on the twins’ original zygosity.
  • Personal curiosity may lead you to pursue confirmation of twin zygosity.

Identical vs. Fraternal Twins

Identical twins come from one fertilized egg called a zygote. The zygote, which usually develops into one child, instead grows and splits early in development to form two embryos.

Because the twins come from one egg and one sperm, they have exactly the same DNA and are, therefore, identical twins.

Fraternal twins, on the other hand, develop when there are two different eggs in the mother’s womb that are fertilized by two different sperm. Fraternal twins will not have the exact same DNA, although like other siblings, they can be expected to share some of the DNA they inherit from both parents.

Need More Information?

For more information about twin zygosity testing, please call DNA Diagnostics Center at 1-800-798-0580. You can speak with a case manager who can guide you through the testing process.

Last Updated: 07/2015