Also Monoamniotic Monochorionic twins are at higher risk for TTTS or Twin to Twin Transfusion Syndrome. TTTS is when twins share the placenta unevenly. The twins themselves are healthy, the placenta is the culprit. One fetus gets too much blood and may die of heart failure and the other fetus gets too little blood and may die of anemia. The yolk sac become the placenta.
Some identical twins are mirror twins.
They have mirror image fingerprints, one is right-handed the other left handed and the whorls in their hair go opposite directions. Most conjoined twins are also mirror twins. Polar body twinning occurs when a egg splits prior to fertilization and each half receives a separate sperm. Twins of Two Two eggs are released by the ovaries and each egg is fertilized by a different father. Terminology zygote - fertilized egg.