How to conceive twins? Types, factors, features details about twins

How to conceive twins

The frequency of twins varies across the world and in history. So the question arrived How to conceive twins? In Niger, one person in 12 is a twin, while in Asia, one speaks of one in 70. Scientists have also observed that the rate of twins decreased between 1900 and 1980 and finally increased again from this moment . These variations of course raise questions. What factors could favor the birth of twins?

Let us first distinguish the real from the false twins. When conceiving real twins, a single sperm fertilizes a single egg. The embryo thus formed then divides into two to generate two babies who share the same genes entirely. On the contrary, for false twins, two separate eggs are fertilized by two different sperm.

Scientists still do not fully understand the mechanisms that favor the birth of real twins. To date, therefore, we have not identified with certainty maternal or environmental factors that could increase their frequency. The situation is however clearer for false twins

How to conceive twins?

To conceive false twins, two eggs have to develop during the same menstrual cycle. Normally, an ovum is created by the maturation of a follicle on the surface of the ovary. It is a hormone called FSH, secreted at the start of the menstrual cycle, that triggers its development. When the follicle gives birth to an egg, it also makes a hormone that blocks the production of FSH.

Under these conditions, a single follicle will succeed in producing an egg. However, if the amount of FSH is too large or if it remains elevated for too long, two eggs may appear. It has also been observed that mothers of false twins have higher levels of FSH.

Three specific factors would really favor the birth of false twins: heredity, the age of the mother and the number of children of the mother before conception.


A twin’s sister would be 95% more likely to conceive of twins. Scientists believe that several genes could be responsible for this familial predisposition. In particular, mutations in the genes necessary for the production of the hormone FSH, serving to block its production or capable of reacting to its presence are the main suspects.

Maternal age:

Between the ages of 15 and 35, the chance of conceiving twins is multiplied by four. Scientists suggest that it would be the number of follicles that would explain this situation. When a woman is young, several follicles would be ready to respond to the FSH signal and therefore quickly block its secretion. However, as the woman ages, the follicles become fewer and react more slowly. FSH is then secreted longer, which would allow two eggs to develop. This is also why the frequency of twins has been increasing since 1980. Although fertility treatments could have a role to play, it would be mainly because mothers now have children at an older age.

The number of children:

The more children a woman has at the time of conception, the greater her chances of having twins. It is also believed that the drop in the rate of twins between 1900 and 1980 could be explained by the disappearance of large families.

Other factors:

Certain factors have been associated with the birth of twins, but they are sometimes controversial. Among others, we find the size of the mother, her body mass index, the season of conception, smoking, the use of hormonal contraceptives and folic acid supplements.

The special case of babies

conceived during breastfeeding Could having a baby while breastfeeding increase the chances of having twins? According to Dr. Steinman, this would be the case . In 2001, he studied mothers attending La Leche League who had become pregnant while breastfeeding. He thus calculated that the percentage of birth of real twins was 3.6% among these mothers whereas in a randomly selected population, we speak rather of 0.4%. For false twins, the frequency was 7.8%, compared to 0.7% in general.According to Dr. Steinman, nursing mothers have lower levels of calcium.

How to conceive twins
How to conceive twins? Types, factors, features details about twins

As calcium is needed to bind cells together, a drop would weaken the strength of the links between the cells of the embryo. It would therefore be more likely that it will split in two to give birth to real twins. In addition, breastfeeding disrupts the secretion of sex hormones. This could lead to overproduction of FSH and promote the conception of false twins.However, this is the only study to link breastfeeding to the conception of twins.

First theory

Contacted on this subject, Dr. Jacques Kadoch, head of the department of reproductive medicine and biology at the University of Montreal Hospital Center, said he was surprised by these data of which he had never before known.This hypothesis must therefore be analyzed in more depth before it can be concluded that breastfeeding increases the chances of conceiving twins.In Quebec, in 2010, births of twins represented 3% of all births .This post was first published on the Maman Éprouvette site .

This article “How to conceive twins?” comes from the blog kcouillard and Quimamme

Monovular or monozygotic twins come from a single fertilized egg divided into two, which gives rise to two different embryos. For this reason  , twins are also called monozygotic or monovular.

It is important to distinguish monozygotic twins from heterozygotic twins . The latter, unlike the monozygotes, are formed directly from different eggs and each of them is fertilized by a different spermatozoon. Twins can also be called bizygotes, dizygotes or biovular.

What is the difference between monozygotic and heterozygous?

First, it is important to clarify that the terms “monozygotic” and “heterozygous” mean very different things:

Monozygotes are those twins that come from the same egg  and, once fertilized by sperm, divide into two, thus giving rise to two different embryos. For this reason, twins are also known as monozygotic or monovular.

The heterozygotes, on the other hand, are formed directly from different eggs  and each of them is fertilized by a different spermatozoon. They are also known by the name of bizygotes, dizygotes or biovulars.

In the case of monozygotes, the genetic information is exactly the same, which is why they are “identical twins”. However, the degree of similarity between them can be the same as in heterozygous twins.

What are the chances of having them?

Twin pregnancies are much more frequent in assisted reproduction treatments because,  to increase the success rate, two or three fertilized eggs are implanted in the uterus . It is likely that none of them will thrive or only one, but if both, or all three, will do, the pregnancy will be multiple.

Even  drugs that induce ovulation increase from the 30-35%  chances  of having twins . In other words, about one in three gestations obtained with assisted reproduction techniques are multiple.

The cases of monozygotic twins,

however, have nothing to do with this type of techniques and drugs since the division of the zygote is caused by a biological “accident”. For this reason, the odds may be the same as for spontaneous pregnancies.

Finally, it should be borne in mind that, if twin pregnancies are rare, trigeminal pregnancies are even more so. The SEF calculates that the percentage is only 0.012%, or one out of 8,100 gestations.

twins baby
monozygotic twins

Even when assisted reproduction treatments are performed or ovulation inducing drugs are administered, the probability is low: one in 700 pregnancies, which corresponds to 0.14%.

Factors related to the birth How to conceive twins

Several studies have linked the following factors to the probability of conceiving twins:

  • Age of the mother . Women over the age of 35 are more likely to have multiple pregnancies since an increase in ovarian follicular stimulation occurs after this age which causes the follicles to generate more eggs. It is a bit paradoxical since, at these ages, the chances of conceiving are lower. An estimated 70% of women over 45 have twins.
  • The weight of the mother . The American Congress of Obstetrics and Gynecology, in a complex study, reported that a body mass index equal to or greater than 30 is a factor that promotes polyiovulation. An increased probability was also found in tall women.
  • The ethnic group of the mother . A scientific study conducted in the United States has shown that black women are more likely to have twins than Caucasian women who, in turn, are more likely than Latinas and Asians.  
  • Genetic inheritance . Having a history of multiple pregnancies in the family increases the odds. It is estimated that 17% of twins also have twins. The inheritance is transmitted both by the father and the mother, but it is obviously expressed only in women because they ovulate.

Types of twin pregnancies – How to conceive twins

First, it is necessary to differentiate a monovular twin pregnancy from a biovular pregnancy and several cases may occur:

  • Bicorial-biamniotic pregnancy : there are two placentas and two amniotic sacs. It is multiple pregnancy with fewer risks and occurs in 30% of cases.
  • Monochorionic-biamnotic pregnancy : there are two separate amniotic pockets, but only one placenta. It is a pregnancy with multiple risks, since fetal-fetal transfusion syndrome can occur, that is, one of the two children absorbs all the “resources”, even those of the other. It occurs in 63% of monozygotic pregnancies.
  • Mono-amniotic pregnancy : occurs when babies share the placenta and amniotic sac. It is the least common case of all and the one with the highest risk.
  • Siamese : they share the placenta, the amniotic bursa and some parts of the body. This phenomenon occurs because cell division took place 13 days after fertilization.

Features of twin pregnancy – How to conceive twins

On average,  the twin pregnancy lasts less than the pregnancy of a single child  since the two fetuses, as they grow, run out of available space more quickly and the placenta can age earlier.

This type of pregnancy  requires the same examinations and tests as a single child’s pregnancy, with some ultrasound scans  more than the usual three of the “single” pregnancy.

In twin pregnancy, the mother’s diet plays a fundamental role. Mom should increase calorie intake by about 300 a day , but in a healthy way:

  • It is necessary to increase the consumption of fruit and vegetables.
  • It is also necessary to increase the intake of proteins, essential for the development of fetuses: white meat, fish (the blue one is ideal for its intake of Omega 3), eggs and legumes.
  • The need for iron also increases, as the mother’s body must use its reserves in order for blood with oxygen to reach the fetuses.
  • Folic acid is also essential, especially in the first three months of pregnancy: spinach and other green leafy vegetables, whole grains and fish rich in omega 3 (salmon, mackerel, sardines, etc.).
  • Calcium is another essential mineral in pregnancy but, even more so, in a multiple pregnancy.

Siamese twins – How to conceive twins

Siamese are twins who have not completely separated in the womb . The binding occurs due to a problem in the development of monozygotic embryonic cells.

Cell division occurs later and the more time passes, the more organs are shared. It is not a genetic defect, but a mutation that occurs during the development of the embryos.

Why are they called Siamese? This term originated in the mid-nineteenth century and became international due to the fame of the case of the brothers Eng Bunker and Chang, born in Siam (Thailand) united by a cartilage between the chest and the abdomen.

What are the causes? Nowadays there is no scientific explanation. The most widespread theory is that of fusion, which causes the late separation of the embryonic plaque, which is why the monozygotic twins who have not separated in the first weeks may be born united in some way.

The cases are very few. Only one birth in 200,000 is Siamese.

What will breastfeeding look like in these cases?

If you have twins, breastfeeding is more complicated, but not impossible . With a little effort, practice and a lot of patience, the result will be positive and of great satisfaction for you and your little ones. We give you some practical tips to serenely breastfeed your twins.

  • During the first weeks of life , babies will require breastfeeding every half hour. It will be a difficult phase because you will have the feeling of not doing anything other than breastfeeding. Gradually, you should get your kids used to taking milk at the same time. How to do it? You should gradually synchronize their rhythms. Whenever the hungrier asks for the breast, you will also give it to the other. In this way, their feeds will be contemporary and will end up being hungry at the same time.
  • Supporting both children at the same time is not easy . With the help of two pillows this task will be easier. You should sit in a comfortable place, place the two cushions on your legs and place the children on them.
    Hold the cushions and babies with both arms, positioned so that the little ones reach the nipple on their own. You can rest your feet on a cushion that allows you to lift your legs and feel more comfortable.
  • If you have twins,  the diet must be richer  from an energy point of view: compared to the basic amount of about 2,000 calories per day, the supplement should vary between 900 and 1,200 more calories.
  • Remember to alternate the breasts  between the babies. Do this every 24 hours, so it will be easier for you.

How to treat identical twins? – How to conceive twins

The bond between the twins  is an indispensable element for their growth. When they are very young, they must be together , as they have shared a very small space for months. Therefore, they must be in the same cradle next to the mother, without separating them, unless there is a medical need.

Remember, however, that such an exclusive and lasting relationship, especially if they are monozygotic twins, can compromise the individuality of the two children. We must therefore avoid certain attitudes that can lead us to consider twins as an inseparable unit.

How to conceive twins
How to treat identical twins?

First of all, we should avoid giving them too similar names and we must turn to them with the “you” and not with the “you” , calling them by their name and avoiding referring to them with the generic term “the twins”. To make them recognizable to others, their initials can be embroidered on their clothes or friends can be informed of a particular characteristic or a garment that distinguishes them.

  • One should avoid considering or commenting on their similarity in their presence, as well as using them to surprise friends and strangers.
  • We must evaluate the character differences of each of the twins, to avoid labeling them with predetermined adjectives: the big or the small, the extrovert or the shy.
  • Different gifts should be chosen, trying to strengthen each individual’s individual tastes.
  • However,  in the effort of diversification and autonomy of children, we must not exclude all possible experiences in common , so as not to break the delicate bond that unites twins and avoid aggravating the anxiety of separation that affects all twins in the early years of life. Occasionally, you have to let them play or dress the same way, as well as do the same things.

And the different twins?

In the case of different twins, the same attitude considerations that we saw in the case of identical twins apply. All twins, brothers born together, in fact tend to be considered a multiple unit, instead of being treated as individuals . 

Curiosity about monozygotic twins – How to conceive twins

“It’s two drops of water!”. The extraordinary similarity between the monozygotic twins always arouses our admiration. But is this similarity the same in all senses? For example: do they smell the same? Do they have the same dreams? Is their immune system identical? To what extent do they look alike? Here are some curiosities about twins.

  • Monozygotic twins also look alike in the immune system . For this reason, in many cases, they get sick in the same way and at the same time. Scientific research has shown that out of nine types of antibodies, twins born from the same egg have seven equal ones, while the average for other children varies from six to four.
  • They have similar dreams : say the twins Giorgio and Nicola Pressburger, writers and directors, who wrote a novel about one of their dreams, “The green elephant”.
  • They smell the same : not even the best police dogs can distinguish the smell of a monozygotic twin from another. Sometimes, fingerprints are the same too.
  • They confirm the theory of chronogenetics : according to this science, our life is regulated by rhythms related to time.
    Luigi Gedda, author of the Mendel Institute for the study of twins, formulated this hypothesis after years of collecting data relating to twins from all over the world. An example is the case of John and Arthur Mowforth, two retired airmen: at the age of 70, they suffered from chest pain on the same day and died just over an hour apart.
  • They have a sort of telepathy : in an experiment conducted at the Language Center in San Diego, California, 14 pairs of identical twins were divided into separate rooms, so that they could not communicate. In 12 out of 14 cases, when a twin was asked to make a gesture, like raising his arm, closing his eyes or yawning, the other also did it.
  • Usually he likes the same names : Tom Bouchard, an American psychologist specialized in the study of twins separated at birth, cites, among the various examples, that of twins Dorothy Lowe and Bridget Harrison, adopted in the first days of life by two different families. When, after years of separation, they met, they discovered that they called their children in a surprisingly similar way. The firstborn had been baptized, Andrew Richard and Richard Andrew, and the second daughters Karen Louise and Catherine Louise, respectively.

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