Do identical twins have to look alike?
As the mother of “identical” twins, I can assure you that they are NOT necessarily identical. The term identical is misleading and inaccurate. The accurate term is monozygotic, meaning from one zygote or fertilized egg. Depending on when the zygote divides, monozygotic twins may be dichorionic/diamniotic, meaning that they have separate placentas and amniotic sacs, or monochorionic/diamniotic, meaning sharing a single placenta but having separate amniotic sacs, or monochorionic/monoamniotic, meaning sharing the same placenta and amniotic sac. While certain features will certainly be the same (eye color, hair color, basic body shape, etc), variations in placenta blood flow, twin to twin transfusion, interuterine growth restriction, and position in the womb can differences in the twins appearance even before they are born. Additionally, studies have shown that gene expression (the activation of certain genes) may cause monozygotic twins to have differences in appearance and even medical
