When a woman receives the news that she is pregnant, there are many questions that cross her mind. Everything will be OK? Will it be a boy or a girl? And if more than one baby comes? This last case is rare, but quite a surprise for future parents. It will be in the ultrasound that you perform in the first weeks of pregnancy when you discover if you have a multiple pregnancy.
Now, although we generally distinguish multiple pregnancies as identical or fraternal twins, we don't always know exactly what the differences are between them. In fact, these are not the only two types of multiple or twin pregnancies that exist. Depending on different issues, they are classified into one type or another, which will interfere with the proper development of the pregnancy.
Popularly known as twins, dizygotic twins are those in which the ovary has released two ovules and both have been fertilized by each sperm. These babies will share your gestation, but not your genetics. Therefore, they may or may not be of the same sex and, although they may physically resemble each other, they will not be identical.
Each of the fetuses will grow in its own placenta and its own amniotic bag, therefore, it is common for them to develop more than those that are univiteline. Generally, this is the type of multiple pregnancy with the fewest complications.
We are here with the so-called identical twins. In this case, it is a single egg, fertilized by a single sperm. However, the zygote (already fertilized egg) splits in two, giving rise to two fetuses with identical genetic makeup. That is to say: they will be of the same sex and physically equal, although they may present subtle differences between them.
However, monozygotic twins are also divided, in turn, into more types depending on when the zygote divided: they can be dichorionic or monochorionic, as well as diamniotic or monoamniotic.
In this case, each twin grows in its own placenta, the organ in which the fetus develops, communicating with the mother through the umbilical cord. In this way they obtain their oxygen and nutrients from the mother. Furthermore, each grows in its own amniotic sac.
Here the twins share the same placenta, but each is developing within its own amniotic sac.
This is the rarest case, in which twins share both the placenta and the amniotic sac. In this circumstance, complications are more likely.
