ATTENTION

If you or someone you know is experiencing a mental health crisis, call 988 for 24/7 free and confidential crisis support. You do not have to be suicidal to call. Access more info and resources on suicide prevention, emotional and mental health support

toggle mobile menu Menu
toggle search menu

Site Navigation

Supplemental

Menu

Twin pregnancy types

Twin pregnancy types

Twin pregnancy types.

Identical twins come from a single egg that has been fertilized by one sperm. For unknown reasons, the fertilized egg splits into two embryos during the first stage of development. In the uterus, most identical twins share the same placenta. (They get oxygen and nutrients and get rid of wastes through the placenta.) But they usually grow within separate amniotic sacs. In rare cases, identical twins share one amniotic sac.

Fraternal twins develop when two eggs are fertilized by two separate sperms. The fetuses have separate placentas and amniotic sacs.

Current as of: July 10, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. Healthwise is a URAC accredited health web site content provider. Privacy Policy. How this information was developed to help you make better health decisions.

© 1995- Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.