Are My Twins Identical or Fraternal?

Identical or fraternal twins

Twin Zygosity

If you are pregnant with multiples, you know that you’ll soon face unique joys and challenges that may not accompany the single birth experience. With twins, a common question that parents have is whether the twins are identical or fraternal. DNA Diagnostics Center offers a Twin Zygosity DNA test that definitively shows whether twins are identical or fraternal.

A Twin Zygosity test compares the twins’ DNA profiles to see whether they match—an exact match proves that the twins are identical. When twins are born, the physician usually is able to tell whether twins are identical or fraternal by examining the placenta; identical twins usually share a placenta, while fraternal twins are usually in two different placentas. However, there are many reasons to consider a Twin Zygosity DNA Test in addition to placental inspection.

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. 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 emerge as the twins grow, casting doubt on an original zygosity determination earlier in life.
  • Personal curiosity.

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

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 exactly the 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 to speak with a case manager who will review the information you provide and can guide you through the testing process.