Doctors refute the prevailing opinion that twins are brothers or sisters with the same appearance, who were born at almost the same time to the same mother, while twins born under similar conditions differ in appearance and have a different gender. It turns out that all babies born in the same pregnancy are twins. However, there is still some difference.
Features of the biology of twins and twins
Modern medicine cannot fully explain the twin phenomenon. There are three options for the development of pregnancy, leading to their appearance. In the first case, the egg begins to divide after fertilization with one sperm into several parts. As a result, identical or identical twins are born, which, when carried, had either a common placenta and a fetal bladder, or a separate placenta and a fetal bladder.
Also, each twin can develop in his fetal bladder, while having a placenta in common with his brother / sister.
The second option is monozygous or semi-identical twins, who are born quite rarely and as a result of a difficult pregnancy. The polar body of the egg usually dies off before fertilization, but in this case this does not happen, and, after one or two sperm have entered, a second child develops in it.
And finally, the third option - the birth of dizygotic twins - is possible when two eggs are fertilized with two sperm. Such twins coincide in the set of genes by about 50% and during pregnancy develop in separate fetal bladders and placentas.
External features of twins and twins
So what's the difference between twins and twins? Identical twins with the same set of genes have the most similar appearance. They have the same blood type, gender and fingerprints. It so happens that a certain number of identical twins (about 25%) are born with an interesting difference - a mirror image.
Mirror similarity is a complete identical similarity of two twins, the appearance of which absolutely repeats the appearance of each of them.
Semi-identical (monozygous) twins, with all the external similarity, can be born heterosexual, while dizygotic twins, which are twins, look like ordinary children from the same parents. Also, twins can be heterosexual or same-sex.
According to the medical point of view, twins are both twins and triplets - in other words, all babies born in the same pregnancy are considered twins. Their main difference is determined by the type of fertilization (identical, semi-identical, dizygotic) and external similarity - twins are as similar as possible, and twins differ in appearance, having only similar external features.
