Getting pregnant with twins is the dream of every couple, because this way female friends only need to endure the pain of childbirth once to have two babies, be companions to each other, and no longer have to worry about having a second child. Since we want to conceive twins, first we need to understand the principle of twin formation.
Classification of Twins
1. Homozygotic twins: Due to the separation of a fertilized egg into two or more independent embryonic cells or cell populations during the division process, they develop into different individuals. The twins produced by this division have the same genetic characteristics, therefore, they are of the same gender and have similar personalities and appearances.
2. Heterozygotic twins: Two follicles simultaneously or sequentially release mature eggs, which are fertilized simultaneously or sequentially. Because the embryos come from different eggs and sperm, they have different genetic characteristics, and the babies born may have different appearances and genders (i.e. twins). Most twins (about 75%) belong to this category.
The principle of twin formation
Twins are divided into two types: dizygotic twins and monozygotic twins. The reason for the formation of twins is that two eggs are fertilized simultaneously to form two fertilized eggs, which are then implanted into the decidual layer of the uterine wall and develop into twins. This type of twin consists of two fetuses with separate placenta, chorion, and chorion. The blood circulation between the two placenta is not connected, and the two fetuses reside in their respective gestational sacs. There is a septum composed of two amniotic membranes and two layers of chorion between the two amniotic membranes. The twins can be of the same or different sex and blood type, and their faces are the same as those of their brothers and sisters.
Monozygotic twins are formed by the division and development of one egg after fertilization. The characteristic of monozygotic twins is that they consist of two amniotic sacs and a common placenta and chorion. The fetuses live in their own amniotic sacs, and the septa between the two amniotic chambers are only composed of two single-layer layers. The blood circulation of two fetuses is interconnected through the placenta. Therefore, monozygotic twins have identical blood types and genders, and their appearance is also difficult to distinguish.
Probability of twins
Having twins is related to genetics, race, medication, and other factors. The country with the highest probability of having twins in the world is 15%, while the probability in China is around 5%, and the probability of having twins is much smaller.
Twins are identical twins, while twins are fraternal twins. The so-called monozygotic twins refer to the situation where a fertilized egg divides into two embryos during fertilization, with the same sex and genes, and the probability is extremely low. Heterozygotic twins refer to the situation where two egg cells implant in the female uterine cavity during fertilization, and fertilization occurs simultaneously, forming two embryos with their own placenta and different genes. When one of their genes is xy and the other is xx, they are twins. When two embryos have the same genes, the probability of being fraternal twins is also very low. The appearance of fraternal twins is different. Different from identical twins.
From this, it can be seen that having a pair of twins is certainly beautiful, but twins are still a rare event. In China, the probability is only 0.5%, and it is also closely related to genes. Therefore, if there is no twin gene in the ancestors, it is better to prepare for pregnancy obediently. Whether it is twins or singletons, they are both precious to parents.
