What you need to know about types of twins

These days, the birth of twins is a bit more common than before. Maybe you have twins in your family or among your friends. When you find out that you are having twins, you feel a great joy and a little curiosity. Almost everyone knows only about identical twins and fraternal twins. But there is actually more behind these two types. Okay, let's talk about the wonderful world of twins in a simple way.

The two main ways to conceive twins

There are two main ways in which twins can be conceived. Doctors call these ``Dizygotic'' and ``Monozygotic''. In layman's terms, these are twins who look different and twins who look the same.

• Fraternal/Dizygotic twins: This occurs when two eggs are released from the mother's ovaries at the same time and fertilized by two separate sperm from the father. In other words, it's like two conceptions happening at the same time.
• Identical/Monozygotic twins: This is when a single egg, fertilized by a single sperm, splits into two within the first few weeks of conception . This is because the two babies appear identical because the same embryo splits in two.

Meanwhile, fertility treatments, especially technologies like IVF, can sometimes lead to twins that are a little different from these traditional methods. Doctors call these "atypical twinning." These are very rare.

Who are these identical twins? (Monozygotic Twins)

These are the "identical twins" we all know. About a third of all twins in the world belong to this type.

As I said before, these children are created by the fertilization of a single egg by a single sperm, and then the embryo splits into two. Therefore, their genetic information, that is, their `DNA`, is 100% identical . That is why they look and feel the same.

Sometimes these twins can share the same amniotic sac in the womb. This is determined by the time the embryo splits. Another surprising thing is that some identical twins are like "mirror images." That is, what is on the right side of one child is the same as on the left side of the other child. For example, if one is right-handed, the other may be left-handed. In fact, why a fertilized embryo splits in two is still a mystery to medicine.

What about twins who look different? (Dizygotic Twins)

This is the most common type of twin. About two-thirds of all twins are of this type. We also call them "Fraternal twins ".

This is where two separate eggs are fertilized by two separate sperm. Therefore, these children have only 50% of the same genetic information (DNA). To be precise, they are like two normal siblings born at different times .

Because of this,

• They don't have to look the same.
• They don't even have to be the same sex. That is, if there are twins that are a girl and a boy , they are definitely ``Dizygotic`` twins.
• They have separate placentas and separate amniotic sacs in the uterus.

How do you know for sure if twins are identical or different?

This is a problem that many parents have.

• If your twins are a girl and a boy , no problem. They are definitely `` Dizygous`` or different twins.
• But if both are of the same gender , that is, both are boys or girls, the story is a little more complicated.

Ultrasound scans during pregnancy, especially after 14 weeks, can give doctors some idea of ​​the baby's placenta. But they are not 100% accurate.

Sometimes, when babies are born, they look at the placenta and say, "These are identical twins," but as the babies grow up, they start to look different. It can also be the other way around. So, if you want to know for sure, the best thing to do is to get a `DNA` test.

Extremely rare types of twins that are surprising to hear about

You probably haven't even heard of these because they are very, very rare.

• Semi-identical twins `(Sesquizygotic)`: This occurs when a single egg is fertilized by two sperm. This is very rare, as normally no embryos formed in this way survive. These children can have between 50% and 100% of their DNA identical. Surprisingly, these types of twins can also be of opposite sex.
• Vanishing Twin Syndrome: This is not actually a type of twin, but something that happens during pregnancy. When two twins are conceived, one of the fetuses stops developing and is absorbed into the mother's body or the other fetus.
• Fetus-in-fetu: This means "fetus within a fetus." This is a parasitic twin condition. The undeveloped fetus of the other twin is found inside the body of a healthy baby. This is also extremely rare.
• Superfetation and Superfecundation: These are also extremely rare phenomena. `Superfetation` is the occurrence of another conception while a woman is already pregnant. `Superfecundation` is the fertilization of two eggs released during the same ovulation cycle by sperm from two different men. Much is still being scientifically discovered about these.

Don't worry about these rare types. Because the probability of these occurring is very low. Most often, we encounter twins of the two main types we talked about earlier.