Are identical twins hereditary?

Many people envy others for being able to give birth to two children at once, because they are twins. Moreover, if we look at our parents’ generation, there were also cases of twins. Could it be that identical twins are hereditary? We also found that this problem is quite common. Some people seem to have twins very easily, and this situation is indeed closely related to genetics. If there are twins in the family, the same possibility will exist for the next generation.

I have heard of a strange story before about a family with three generations giving birth to twins. Could it be that twins are really hereditary? If so, what is the probability of twins giving birth to twins again?

The chance of a female fraternal twin giving birth to fraternal twins is about one in fifty-eight, and is related to the genetic factors that cause fraternal twins. The chance of a male fraternal twin being born is about one in 116, but is affected by many factors, such as the age, height, and weight of the spouses. Among these twins, the probability of identical twins is about one in 250 all over the world; the probability of fraternal twins depends on geography, about six in a thousand in Europe and North America, about one in a hundred among black Americans, and about four in a hundred among black Nigerians.

In addition to genetic factors, there are other ways that may increase the chances of having twins. A Swedish medical research institute recently pointed out that women who take folic acid have nearly twice the chance of conceiving twins than women who do not take it. It is reported that Swedish researchers have been studying and analyzing the information and data on the medications taken by local pregnant women since 1994. They found that among 2,569 pregnant women who had taken folic acid, 2.8 out of every 100 children they gave birth to were twins, while among pregnant women who did not take folic acid, the ratio was 1:5.

The formation process and characteristics of identical twins

Like all fetuses, identical twins start out as a single-cell fertilized egg that contains 23 pairs of chromosomes. Among them is a rare phenomenon. A few days after conception, the blastocyst splits into two. Each new blastocyst is composed of the same chromosomes, and the chromosomes carry the same arrangement of genes. At this time, the two blastocysts may develop into identical twins. The outer membrane of the blastocyst is called the zona pellucida, and the inner lining is called the trophoblast, which is only one cell layer thick and will eventually become the placenta. The trophoblast contains the inner cell mass, which are the supporting stem cells that will eventually become the fetus. Periodically, the connection between some cells and the trophoblast membrane weakens, allowing fluid to leak out and causing the trophoblast to collapse, which then repairs itself. But two of the eggs allowed the embryologists to see something that no one had ever seen before: after the membrane collapsed, the inner cell mass separated into two clusters, each of which would attach to a different side of the trophoblast when the trophoblast expanded again. If these cell clusters could develop in the uterus, they would eventually become identical twins.