What’s the difference between identical and fraternal twins?

Twins are the most commonly-occurring multiple gestation and are either identical or fraternal, according to the American Congress of Obstetricians and GynecologistsOff Site Icon (ACOG). Identical twins develop from one fertilized egg and can share the same placenta and have two separate or, rarely, one amniotic sac; fraternal twins develop from two separate eggs and grow in their own amniotic sac, according to the ACOG.

Identical twins have the same DNA, and are usually expected to develop at the same rate during the gestation period, according to the U.S. Department of Health and Human Services Office on Women’s HealthOff Site Icon (HHS).

Fraternal twins have individual DNA and can develop differently, according to the HHS. Fraternal twins are no more alike than any other siblings, and this type of multiple gestation can be a particular concern for health care providers because of their varying developmental rate, according to the HHS.

For more information about identical and fraternal twins, talk to your doctor.

Learn more: