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 mother's womb (uterus), most
identical twins share the same placenta. (They get oxygen and nutrients from
the mother and get rid of wastes through the placenta.) But they usually grow
within separate amniotic sacs. In rare cases, identical twins share one
Fraternal twins develop when two eggs are fertilized by two separate
sperms. The fetuses have separate placentas and amniotic sacs.
July 8, 2011
Sarah Marshall, MD - Family Medicine & William Gilbert, MD - Maternal and Fetal Medicine
How this information was developed to help you make better health decisions.
To learn more visit Healthwise.org
© 1995-2013 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.
We are happy to take your appointment request over the phone, or, you may fill out an online request form.
Disclaimer: The information on this website is for general informational purposes only and SHOULD NOT be relied upon as a substitute for sound professional medical advice, evaluation or care from your physician or other qualified health care provider.