The difference between twins and twin boys and girls

Many friends do not understand the differences between twins and male-female twins, mainly because they think that male-female twins are also twins. This understanding is actually a misunderstanding. Twins are identical twins, while boy-girl twins are fraternal twins. However, there is a huge difference between the two from a biological point of view. Twins are born with the same appearance and gender, but male and female twins are different.

Twins are identical twins, while boy-girl twins are fraternal twins.

Twins are twins of different sexes, also known as fraternal twins. During fertilization, two eggs implant in the female's uterine cavity and fertilization occurs at the same time, forming two embryos. These two embryos have their own placentas and different genes. When one of their genes is xy and the other is xx, they are boy-girl twins. Only in this situation can boy-girl twins appear. The gender and blood type of fraternal twins can be the same or different, and their appearance is the same as that of normal siblings.

Identical twins are composed of two amniotic sacs and a common placenta and chorion. The fetuses each live in their own amniotic sac, and the septum between the two amniotic cavities is composed of only two single layers. The blood circulation of the two fetuses is connected through the placenta. Therefore, the blood type and gender of identical twins are exactly the same, and their faces are difficult to distinguish.

2 The chance of twins

Boy-girl twins are twins of different genders, that is, fraternal twins. Only in this situation can boy-girl twins appear. There is a 50% chance of fraternal twins becoming boy-girl twins. The characteristic of identical twins is that the blood circulation of the two fetuses is connected to each other through the placenta. Therefore, identical twins have exactly the same blood type and gender, and their faces are difficult to distinguish. Having twins is related to genes, race, drugs, etc.

The country in the world with the highest probability of giving birth to twins is 15/1000, while the probability in my country is about 5/1000, and the probability of giving birth to twin boys and girls is much smaller.

3 How many placentas do twins have?

Generally speaking, male and female twins have two placentas, while twins have one placenta. The number of placentas for twins depends on the situation. Generally speaking, fraternal twins have two placentas. The difference between identical twins depends on the time of differentiation, but generally speaking, identical twins have the same placenta. However, only fraternal twins can produce male-and-female twins (except for genetic mutations), so male-and-female twins have two placentas.

4 Health Tips

Seeing this, I believe everyone has a certain degree of understanding of the difference between twins and boy-girl twins. The probability of twins and boy-girl twins is very small, so whether in China or abroad, the arrival of twins and boy-girl twins is a great thing, and you must cherish them!