According to the American Academy of Pediatrics...
Twins - are developed when two different eggs are fertilized by two different sperm cells to produce two genetically different babies. They are called "fraternal" twins and represent about 90 percent of multiple births. Twins develop in two separate amniotic sacs.
Identical twins - occur when one fertilized egg splits and forms two babies who have the same genes, so they look alike and are the same sex. Identical twins share the same amniotic sac.
What you didn't know
- A woman's chances of having identical twins are not related to age, race or family history. So, it can happen to anyone.
- A woman's chances of having fraternal twins is increased if there are fraternal twins in the family history.
- Black women have the highest chance of producing fraternal twins.
- Contrary to popular belief, having twins does not skip generations.
- Women in their 30s and 40s have a greater chance of producing twins.
- Boy/girl twins are always fraternal twins, whereas identical twins are always of the same sex.
And now you know more than you did before about twins!
Read more at www.healthychildren.org/English/family-life/family-dynamics/Pages/The-Difference-Between-Identical-and-Fraternal-Twins.aspx