Fraternal twins are also called

Fraternal twins & identical twins

About twins

We usually describe twins according to:

how many eggs they develop from – 1 or 2
whether they share a placenta in their mother’s womb.

The main types of twins are fraternal twins and identical twins.

Most twins are born healthy, but a twin pregnancy can mean a higher chance of health complications for you and your babies. If you're pregnant with twins, you and your babies will need extra check-ups.

Fraternal twins

All pregnancies start when a sperm fertilises an egg. This fertilised egg is called a zygote.

Sometimes a woman’s ovaries release 2 eggs, and a separate sperm fertilises each egg. This forms twins. These twins are called fraternal twins, dizygotic twins (meaning two zygotes) or non-identical twins.

During pregnancy, the developing babies get oxygen and food from their mother through the placentas and umbilical cords. Fraternal twins have separate placentas and umbilical cords. The technical name for this is dichorionic.

Fraternal twins can be the same or opposite sex and their genes are as different as any other brother and sister. Often, same-sex fraternal twins look different. For example, they might have different hair or eye colour. Occasionally they look quite similar.

Fraternal twins happen in about 70% of twin births in Australia.

Very rarely, fraternal twins share a placenta. These types of twins are called chimaeric twins.

Identical twins

Sometimes a fertilised egg splits within a few days of conception to produce genetically identical twins. Because these twins come from one zygote, they’re also known as monozygotic. Identical twins are the same sex.

There are 3 types of identical twins.

About one-third of identical twins split soon after fertilisation and form completely separate twins. Like fraternal twins, these twins have separate placentas.

The other two-thirds split after they attach to the wall of the womb. As a result, they share a placenta. The technical name for this is monochorionic.

In a very small number of identical twins, splitting might happen even later. In this case, both twins share an inner sac, called the amnion, in addition to sharing a placenta. The technical name for this is monoamniotic twins. They’re often called MoMo twins.

Identical twins happen in around 1 in 250 pregnancies in Australia.

Although identical twins have the same genes, they don’t always look the same. This is because children’s health and development are shaped not only by genes but also by experiences in the womb and after birth. For example, a twin who gets less blood from a shared placenta might weigh less at birth.

Sharing a placenta or inner sac: why it’s important to know

Sharing a placenta means that twins share a blood supply during pregnancy. Sometimes the blood supply is shared unequally, which can cause health problems for both twins.

Women who are pregnant with twins sharing a placenta need to be checked more often than women who are pregnant with twins with separate placentas. Frequent checks help to pick up any complications early.

Twins sharing an inner sac (monoamniotic) are also at a higher risk of complications during pregnancy because of the chance that their umbilical cords might tangle and cut off their blood supply. These twins are checked even more closely. Medical professionals often recommend that these twins are born at 32-34 weeks. This is earlier than other types of twins, who are generally born at 37-38 weeks.

Medical professionals use ultrasound to work out how many placentas twins have. The earlier the ultrasound, the more accurately it can say how many placentas there are. It gets harder to work out later in pregnancy. After the birth, medical staff will look at the placentas to check what type of twins they are.

Fraternal or identical: why it’s important to know

Same-sex twins with separate placentas can be fraternal or identical. For health reasons, it’s good to know whether your twins are fraternal or identical.

To find out whether twins are identical or fraternal, you can ask for a genetic test after your babies are born. This is called a zygosity test. The test doesn’t hurt and involves collecting a sample of cheek cells by rubbing the inside of your babies’ cheeks with a soft applicator (like a cotton bud). The cost of this test starts at $199 (for both twins) in Australia.

Identical twins are more likely than fraternal twins to get the same illness. If one of a pair of identical twins is diagnosed with a particular disease or health condition, like high blood pressure, the other twin should be checked often for early symptoms.

Because of their genetic make-up, identical twins will always be compatible for organ transplantation, if they ever need it. Fraternal twins are compatible only sometimes.

Other reasons why twins and parents of twins might want to know whether they’re fraternal or identical include:

trying to work out the chance of having more twins in future pregnancies (only fraternal twins run in families)
making sure they have the right information about their genetic make-up
being able to answer questions from family, friends and others
being involved in twin research
just being curious!

Some identical twins are mirror twins – for example, their hair parts on opposite sides, they are oppositely handed, or they have birthmarks on opposite sides of their body. In some rare cases, their internal organs can be mirror images of each other. It’s not known why some twins are like this.

In very rare cases, twins can be born physically joined together in different ways. These twins, called conjoined twins (previously called Siamese twins), can happen if the fertilised egg splits quite late after fertilisation.

Triplets (1 in 5000 births) and quadruplets (less than 1 in 100 000 births) can develop as a result of combinations of fraternal and identical twinning. There are no reliable figures for quintuplets (5 babies) and sextuplets (6 babies).

More about twins

In Australia, twins happen in 1 in every 80 births. This means that 1 in 40 Australians is a twin.

The birth rate of identical twins is the same around the world and doesn’t vary with the mother’s age.

In contrast, the birth rate of fraternal twins varies widely across countries and can be influenced by the mother’s age. Women aged over 35 years are the most likely to have fraternal twins, because their ovaries are more likely to release more than one egg at a time.

More twins were born from the 1990s to the mid-2000s. This is because it was common to transfer more than one embryo during in-vitro fertilisation (IVF) treatments. The rate of twins from IVF is now lower, because it’s now usual practice to transfer only a single embryo.

Twins - identical and fraternal

Multiple births are more common than they were in the past, due to the advancing average age of mothers and the associated rise in assisted reproductive techniques, in particular the use of fertility drugs. Twins account for over 90 per cent of multiple births. There are two types of twins – identical (monozygotic) and fraternal (dizygotic).

To form identical twins, one fertilised egg (ovum) splits and develops two babies with exactly the same genetic information. This differs from fraternal twins, where two eggs (ova) are fertilised by two sperm and produce two genetically unique children, who are no more alike than individual siblings born at different times. Twins are more or less equally likely to be female or male. Contrary to popular belief, the incidence of twins doesn’t skip generations.

Factors that increase the odds of having twins

Some women are more likely than others to give birth to twins. The factors that increase the odds include:

Advancing age of the mother – women in their 30s and 40s have higher levels of the sex hormone oestrogen than younger women, which means that their ovaries are stimulated to produce more than one egg at a time.
Number of previous pregnancies – the greater the number of pregnancies a woman has already had, the higher her odds of conceiving twins.
Heredity – a woman is more likely to conceive fraternal twins if she is a fraternal twin, has already had fraternal twins, or has siblings who are fraternal twins.
Race – Black African women have the highest incidence of twins, while Asian women have the lowest.
Assisted reproductive techniques – many procedures rely on stimulating the ovaries with fertility drugs to produce eggs and, often, several eggs are released per ovulation.

Fertilisation

Hormones secreted by the ovaries, and a small gland in the brain called the pituitary, control the menstrual cycle. The average cycle is around 28 days. After a menstrual period, rising levels of the hormone oestrogen help to thicken the lining of the womb (the endometrium) and release an egg from one of the ovaries (ovulation).

If the egg is fertilised on its journey down the fallopian tube, it lodges in the thickened womb lining, starts dividing and evolves into an embryo.

Identical or ‘monozygotic’ twins

Around one in three sets of twins is identical. This occurs because the fertilised egg divides in two while it is still a tiny collection of cells. The self-contained halves then develop into two babies, with exactly the same genetic information.

Twins conceived from one egg and one sperm are called identical or ‘monozygotic’ (one-cell) twins. The biological mechanisms that prompt the single fertilised egg to split in two remain a mystery.

Approximately one quarter of identical twins are mirror images of each other, which means the right side of one child matches the left side of their twin.

Fraternal or ‘dizygotic’ twins

Around two in three sets of twins are fraternal. Two separate eggs (ova) are fertilised by two separate sperm, resulting in fraternal or ‘dizygotic’ (two-cell) twins. These babies will be no more alike than siblings born at separate times. The babies can be either the same sex or different sexes, with the odds roughly equal for each.

The proposed ‘third-twin type’

Some researchers believe there may be a third type of twin, although medical opinion is still divided. It is proposed that the egg splits in two, and each half is then fertilised by a different sperm. This theory is an attempt to explain why some fraternal twins look identical.

The normal length of gestation for a single baby is around 40 weeks. However, gestation for twins, either identical or fraternal, is usually around 38 weeks. This shorter time is due to the increased demands on the mother’s body, and the inability of the babies to receive all the nutrients they need in utero.

Since twins are usually premature, they are more likely to have lower birth weights. Prematurity is associated with increased risk of a number of disorders, including jaundice.

Giving birth to twins

Childbirth can give rise to complications when just one baby is present, so twins present extra potential for difficulties. It is advised that women carrying twins give birth in hospital, rather than at home. The babies can be delivered vaginally, but caesarean section delivery may be considered a better alternative in some circumstances.

Zygosity testing

It is difficult to tell if twins are identical or fraternal at birth. Some identical twins may be born with individual sets of membranes, which may lead to the mistaken assumption that the babies are fraternal.

One way to tell the difference is to have the twins DNA-tested. Identical twins share the same genetic information, while fraternal twins share around half. The test can be done with a sample of cheek cells, collected painlessly. Other tests include blood group examinations.

Where to get help

Your doctor
Paediatrician
Maternity hospital

Things to remember

Twins account for over 90 per cent of multiple births.
To form identical or monozygotic twins, one fertilised egg (ovum) splits and develops into two babies with exactly the same genetic information.
To form fraternal or dizygotic twins, two eggs (ova) are fertilised by two sperm and produce two genetically unique children.

Today more twins are born in the world than ever before

March 15, 2021 13:53 Olga Muraya

Most twins in recent years were born in Asia and Africa.
Pixabay Photos.

Since the 1980s, the number of twins born worldwide has increased by a third. Scientists have also found that in some regions of the world, twins are always born more often than in others.

Researchers from the Netherlands, Great Britain and France have studied twin birth statistics for 2010-2015. They found that today in the world one in 42 newborns is a twin, and in total about 1.6 million twins are born every year. Scientists compared these data with statistics 1980s and it turned out that the birth rate of twins has increased by a third since then.

Recall that children born from one pregnancy are considered twins. There may be two or more. Most often, two types of twins are distinguished - identical and fraternal (they are also called twins).

Identical, or monozygotic, twins develop from one egg, fertilized by one sperm, which at some point split into two parts. These twins are called identical because they share 100% of their genes.

Fraternal or heterozygous twins, respectively, result from the fertilization of two eggs by different spermatozoa. Such twins can be of different sexes, and they do not necessarily look like two peas in a pod, because they have only 50% of their genes identical.

Pregnancy in which the mother bears such twins (or more children) is called multiple pregnancy.

The chance of multiple pregnancy increases with maternal age and is also associated with ovulation-stimulating drugs. Today, in vitro fertilization (IVF) is increasingly practiced, as a result of which twins are also often born.

Scientists attribute the rise in the birth rate of twins in the 20th century to the achievements of modern medicine. They believe that in recent years the proportion of twins among newborns has become higher than was ever possible. Therefore, the findings of the current study did not come as a surprise to them.

After examining data from 165 countries, scientists noticed that over the past 40 years, the proportion of newborn twins has declined only in countries in South America. At the same time, approximately 80% of twin births occur today in Asia and Africa. The most interesting thing is that in Africa and at 19The 1980s, and now a record number of twins were born, and their proportion among newborns has hardly changed over the years.

This led scientists to the idea that the population of the African continent has a certain genetic feature that makes women predisposed to multiple pregnancies.

"This is important to note because twin births are associated with increased infant mortality and a high risk of complications during pregnancy, childbirth and postpartum recovery," said study lead author Christiaan Monden, professor at the University of Oxford. ).

Some researchers argue that the proportion of twin births in high-income countries has peaked today and will only decline further. They explain this by the fact that IVF technologies are changing today in the direction of reducing the number of multiple pregnancies. Most women who want to get pregnant still do not want to give birth to several children at the same time, and their desires are taken into account by scientists and doctors.

Sociologists are planning to update the data in a few years to determine whether the birth rate of twins in high-income countries will decline soon. They also look forward to seeing what changes will happen in poorer countries where reproductive medicine (including IVF) is just beginning to develop.

A scientific article detailing this large scale study was published in the journal Human Reproduction.

Earlier Vesti.Ru wrote about how scientists were able to increase the effectiveness of artificial insemination and found out at what age it is best to turn to the IVF method. We also reported that the danger of artificial insemination is just a myth.

science genetics ECO sociology demography twins society news

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So similar and so different

On the last Sunday of May, Twins Day is celebrated all over the world. On the holiday, it is customary to congratulate not only the heroes of the occasion, but also their parents. Raising twins is not an easy task that requires a lot of effort and patience, but all efforts always pay off doubly. After all, few can argue with the fact that it is between the twins that there is an invisible close connection that leads them through life. Today we will tell you about what twins are, what amazing facts are associated with them, and we will reveal the secrets of star brothers and sisters.

Twins, twins and triplets: is there a difference?

“Are you twins? Why don't they look alike?" - moms and dads of twins admit: they have to patiently explain the difference to people almost every day. On the playground or in the store there is always a curious passer-by.

Who are still considered twins?

These are children who developed as a result of one pregnancy and were born in the same birth almost simultaneously. But at the same time, external identity is not an obligatory sign at all.

Twins are monozygotic (identical, identical) and dizygotic (fraternal, twins). Monozygotic twins are formed as a result of the division of one egg. They are genetically identical, they have the same appearance, gender, blood type and Rh factor, only different fingerprints.

Dizygotic twins - they are called twins - are born as a result of the fertilization of two eggs. Twins have a different set of genes, and they look like each other in the same way as ordinary brothers and sisters.

A combination of monozygotic and dizygotic variants is also possible. When two eggs are fertilized first, and then one of them divides into two copies, this is how you get triplets. Triplets can also be only identical - which is extremely rare - and fraternal.

According to statistics, twins are born more often than identical twins. Several factors can contribute to this, such as hereditary predisposition, IVF procedure, mother's age over 35, etc.

Doctors are still arguing about the causes of monozygotic pregnancy. Neither the version of a genetic predisposition, nor the possibility of transmission "by inheritance" is found to be confirmed. It can be considered that identical twins are a real miracle.

Twins in Russia and in the world

The number of born twins is growing every year. Already, every 42nd person in the world has a brother or sister - a twin, in total every year 1.6 million of these babies are born. About a third of them are monozygotic, the rest are dizygotic.

17,227 twins and 213 triplets were born in Russia in 2020. Rosstat also spoke about the most “prolific” regions in recent years: Moscow and St. Petersburg are in first place in this list, Sverdlovsk Region is in second place, Moscow Region is in third place, Tyumen Region is in fourth place, the fifth is shared between the Krasnodar Territory and Tatarstan. Over the past ten years, the maximum number of births of quadruplets was recorded in 2015, when quadruplets were born in five subjects of the Russian Federation - in Kalmykia, Yakutia, as well as in the Kirov, Nizhny Novgorod and Samara regions.

In Russia, there is even a “settlement of twins” — Denisovsky in the Rostov region. In the last 50 years alone, 50 pairs of twins have been born here. In the 2010s, with a population of a thousand people, there were up to 150 twin pairs - now that many have left, there are fewer of them. But still, such a number of twins in one locality is a rarity.

According to research, 30% more twins are born in the world today than 40 years ago. And if earlier African countries were considered world leaders in the birth of twins, today only a little more than 40% of all twins in the world are Africans. And in North America, the number of twin births increased by 71%, in Europe the increase was 58%. In South Korea, twins are born three times more often than 30 years ago. Scientists believe that the reason for this boom is the spread of IVF: the probability of having twins or triplets using this reproductive method is more than 20%. Another reason is that many women began to give birth later, and the likelihood of having twins increases with age.

Star twins

There are also a lot of twins among famous people - and it often happens that both become famous at once. It would seem that competition cannot be avoided, but almost all star brothers and sisters admit that they simply could not have coped without the support of each other.

From school age, the Torsuev brothers Vladimir and Yuri became real stars. After the roles in the film "The Adventures of Electronics" (Vladimir played Electronics, and Yuri played Seryozha Syroezhkina), they were recognized by the whole country. The brothers say that all their lives they seem to feel each other at a distance. For example, when Vladimir had a sharp attack of appendicitis, Yuri, who was a thousand kilometers from his brother, also could not stand on his feet from pain. The fates of the brothers are closely intertwined and even similar, they still work together and even created a musical group.

The famous actresses Olga and Tatyana Arntgolts also talk about a similar connection. There was no question of any jealousy in the profession. Olga recalls how one day she had to start rehearsing the role of her sister, because Tatyana could not take part in the filming. But at the last moment, plans changed, and as a result, Tanya played. But Olga was only happy for her sister. And there were many similar situations in the career of both. Tatyana was born literally a minute earlier than Olga, but she feels like an older sister, she worries about Olya all the time and takes care of her.

The famous Russian football players, the twin brothers Andrei and Vasily Berezutsky, knew from childhood that they would link their fate with sports. After all, their father, a physical education teacher, became the first coach. For 16 years they played for CSKA, they have many victories to their credit. The brothers also ended their careers at the same time and are now engaged in coaching together.

Singer Natalya Podolskaya is very close to her twin sister. Juliana, in order to support her sister, moved to Moscow immediately after Natalia's not very successful performance at an international music competition. Even Natasha's famous husband, musician Vladimir Presnyakov, once admitted that he was a little jealous of his wife for his sister. “My heart is divided into two halves. One of them belongs to Yulia, the other belongs to my husband Volodya," the singer said.

Sisters Dina and Arina Averina are our famous gymnasts. The girls started their professional career at the age of 11. They admit that there is no competition between them, although they compete with each other during their performances at the championships. At the Summer Olympics in Tokyo, according to most fans and experts, the sisters were literally sued: Dina was undeservedly deprived of gold, and Arina was completely left without a medal. Immediately after the end of the competition in Japan, they stated that they were ready to continue to fight and intended to prove themselves in Paris at the 2024 Olympics.

Surprising facts about twins

It is believed that twins are the closest people to each other. There is plenty of evidence that they literally feel each other from a distance. Many myths and legends are built around this wonderful feature. We will tell you about the truthful, but no less amazing facts about twins.

In childhood, almost half of the twins have their own special language. To designate it, even a special scientific term was created - cryptophasia. This secret language can contain not only words or expressions, but also gestures, facial expressions and individual sounds. Scientists believe that most of the words are words distorted beyond recognition that children heard from their parents. Cryptophasia is most often superseded by normal language at the age of 3 years.
Scientists at the University of Nottingham in the UK conducted a study and found that among twins there are more left-handers (17% versus 10%) than among other people.
About a quarter of identical (identical) twins have mirror similarities. For example, one of the kids has a mole on his right shoulder, the other has a mole on his left.
Doctors often talk about the so-called "saving hug" phenomenon - when a healthy brother or sister is placed in an incubator with a sick baby. After some time, the first twin's vital signs improve. Science still cannot explain how it works and what it is connected with.
Twins never weigh the same, even if they were born a few minutes apart.
According to research by Danish scientists, twins live longer than other people. One of the likely reasons for this phenomenon, according to scientists, is a strong social and emotional connection in couples.

Gemini is an amazing phenomenon of nature, thousands of scientists around the world are trying to unravel the secret of their unusual relationship for life. And despite the fact that for parents the birth of such babies is a real test of strength, most mothers and fathers admit that they would never agree to less happiness.