Which genes of mother and father cause twins to become pregnant?

The genetic condition of the parents determines many things in pregnancy, from the physical characteristics the child will have, the health of the fetus, the risk of disease, to the chance that the mother will experience multiple pregnancies. The gene that determines twins is even more unique because it can run in families and not many people have it.

The genes of the mother and father also have their respective roles in multiple pregnancies. Then, whose genes are more dominant so that multiple pregnancies can occur?

The role of parental genes in twin pregnancy

Before discussing whose genes are more dominant in determining multiple pregnancy, you first need to understand what type of twin pregnancy is. The reason is, twin pregnancies are divided into two types, namely:

1. Identical twins

Identical twins, also known as monozygotic twins, occur when an egg is fertilized by one sperm. The fertilization process produces a zygote, but the zygote divides into two different embryos. As a result, two fetuses with the same genetic makeup and sex were formed.

Identical twins are not usually genetic. However, the US National Library of Medicine has reported several cases of families having multiple offspring of identical twins. They had more identical twins than expected.

Allegedly, there are certain genes that affect the stickiness of cells and trigger egg cell division to produce twins. However, this is still a provisional conjecture. The cause of identical twins is not known with certainty.

2. Fraternal twins

Also called dizygotic twins, fraternal twins occur when two eggs are fertilized by two sperm cells during a menstrual cycle. Identical twins can be of the same or different sex. The level of similarity is not as big as identical twins.

Fraternal twins are strongly suspected to be related to genetic factors. There is a gene that triggers the release of more than one egg in a menstrual cycle. In fact, the ovaries normally only release one egg to be fertilized.

This suspicion is reinforced by a number of studies on the odds of fraternal twins. If your mother or sister has fraternal twins, your chances of conceiving fraternal twins are doubled.

Who do the twins' genes come from?

Several scientists from Vrije University Amsterdam, the Netherlands, examined the DNA of 1,980 mothers who gave birth to fraternal twins. In addition, they also examined the DNA of 12,953 people who did not have a family history of twins.

They found that the women had a variation on the so-called geneFSHB and SMAD3 29 percent higher chance of giving birth to twins than women who did not have this variation.

The scientists conducted further research on genes FSHB. This gene stimulates production follicle-stimulating hormone (FSH). The release of FSH triggers the release of an egg from the ovary which indicates the middle of the menstrual cycle.

According to the results of observations, women whose genes function FSHBher changed to have a higher level of FSH in her blood. These women may release two eggs at once, making them more likely to have fraternal twins.

Meanwhile, gen SMAD3 has a smaller role in determining the pregnancy of twins, but this gene helps the body respond to FSH. This is why genes SMAD3 is taken into account as a factor that increases the chance of conceiving fraternal twins.

Referring to the results of this study, it can be concluded that the "twins gene" comes from the mother. The mother's genes do not dominate the paternal genes, but only the mother can release two eggs from the ovaries, allowing fraternal twins to develop.

Can men who are fraternal twins have twins too?

If you are a man with a history of fraternal twins, you likely also have the genes. However, you can't have twins if your wife doesn't have a history of fraternal twins, because the gene isn't in her DNA.

You can't pass the genes for fraternal twins to your wife and make her release two eggs at once. In other words, the genes for fraternal twins will have no effect if they come from the father's side.

You can only pass it on to daughters or granddaughters. This gene will increase their chances of releasing two eggs so that pregnancy can occur.

However, the chance of multiple pregnancies is also influenced by gestational age, race, body weight, and reproductive health history. In order to ascertain its chances in the family tree, you can consult an obstetrician.