Did you know that the probability of having twins naturally is 1.1%? On the other hand, the probability of having twins is much lower, standing at 0.4%. This is confirmed by data from the Spanish Fertility Society (SEF).
In this way, 1 in 90 natural pregnancies will give rise to twins , and 1 in 250, to twins.
And the cases could be more; thus, it is believed that double pregnancies could be more prevalent, but they are not detected because in early stages one of the embryos usually stops.
In this article we talk about the differences between twins and twins , whether or not there is that special connection between twins that is so talked about and what factors increase the probability of experiencing a double pregnancy.
Differences and curiosities between twins and twins
Twins and fraternal twins are born from the same birth . However, twins originate from the same egg and the same sperm (they are monozygotic), and fraternal twins, from different eggs and different sperm (they are dizygotic).
Twins: genetically the same
Thus, in the case of twins, we speak of genetically identical siblings (clones ) who, therefore, will always have the same sex.
This is due to the fact that they come from the same ovum and the same sperm that, at a very early stage of development, divided in two and gave rise to two totally independent individuals.
As a result, they share the same DNA. Although twins are clones, at the genetic level, the environment has its effect on gene expression , and this means that there may be differences between twins.
In this sense, twins have different fingerprints, for example. Thus, although they start from the same genetic base, the environment will operate and may cause certain differences. Also, let’s not forget that they are totally independent people.
Twins: non-identical siblings
On the other hand, in the case of twins, two different ovules and two spermatozoa have caused two births in the same birth.
That is, they are two brothers (genetically different) who were born at the same time.
As they do not share all of their DNA , they can be of different sexes, that is, boys and girls. In addition, physically their differences will be greater than in the case of identical twins.
Interest in the study of twins
The interest in studying twins dates back to 1875, and in psychology there was a key figure: Francis Galton, English scientist and cousin of Charles Darwin.
Galton discovered that year, according to Nancy Segal, a twin and director of the Center for Twin Studies at California State University, Fullerton, “the twin research design, which is a very simple and very elegant way of looking at behavior.”
And it is that, according to an article in the International Journal of Epidemiology, Galton published “the first detailed attempt to use the phenomenon of twins to estimate the relative powers of nature and nurture “.
In fact, studies with twins have been very useful to study the weight of genetics and the environment in personality or intelligence, in certain diseases, etc.
A special connection?
Identical twins often claim to have a connection between them that goes beyond complicity (for example, understanding each other only with looks) or the relationship they could have with other siblings (not twins).
According to the psychoanalyst Melanie Klein (1963), who studied childhood extensively, the fascination with twins stems from the universal fantasy of having a twin brother , and this is linked to feelings of loneliness, the longing for closeness, and the desire to be fully understood.
If we turn to the studies, a 2012 review article, by psychiatrist Tuulikki Trias and Professors of child psychiatry Hanna Ebeling and Irma Moilanen, the twin relationship creates a special kind of relationship , which is that twins can offer each other the other mutual support, companionship and affection.
In this sense, it has been suggested that it is the closest relationship between two people . But it’s also true that identical twins sometimes have to deal with difficult feelings; for example, one can be more dominant.
In addition, sometimes the identification and dependency between the co-twins can be very accentuated and strong.
A special sibling relationship
Trias and colleagues (2012) did a comprehensive review of studies on the relationship between identical twins and concluded that twins generate a special sibling relationship that is different from the single sibling relationship, as well as in different types of twin pairs.
According to the researchers, growing up with the co-twin who is constantly present can be beneficial , although it can also create complicated situations and/or dependency.
Factors that increase the probability of double pregnancies
As a curiosity, there are some factors that increase the probability of having twins. Some of the most relevant are:
Genetics
The chances of having twins, not twins, are doubled when there have been twins in the woman’s family, and different studies have shown this, like this one from 2008.
In this way, although there are many twins in the man’s family, this would not contribute to a greater probability of having twins in his partner.
However, the inheritance that the father transmits to the daughters can influence , that is, the inheritance would also pass through the paternal pathway, but it would only manifest itself in women, since they are the ones who ovulate.
The height
Curious, right? Data shows that taller women are more likely to have twins (as a 2006 study suggests). Experts think this could be related to growth factor and insulin, although why this happens is not fully understood.
mother’s age
Women with a higher maternal age, usually from the age of 38 , are more likely to conceive twins.
This is partly due to hormonal changes as menopause approaches (which would increase the chance of releasing more than one egg during ovulation).
assisted reproductive techniques
The probability increases, specifically to have twins, due to the transfer of more than one embryo.
In the specific case of IVF (In Vitro Fertilization), the rate of twin pregnancies with fresh embryos reaches 12% in women under 35 years of age, and 9% in women between 35 and 37 years of age.
body weight
The odds of having twins increase with a BMI (Body Mass Index) greater than 30 , as suggested by a 2005 study conducted by the American Academy of Obstetrics and Gynecology . Thus, overweight women are more likely to have twins naturally.
In contrast, having a BMI below 18.5 decreases the chance of having twins.
The diet
Diet could also influence the chance of having twins. A 2006 study found that women who ate animal products and foods, especially dairy products , may be taking additional insulin growth factor.
This hormone is released by cows in milk, and when consumed, it would influence human reproduction.
For its part, another study, from 2012, showed that eating a lot of yams (a group of plants with edible tubers) also increased the probability of having twins.
Photos | Cover (pexels), Image 1 (pexels), Image 2 (pexels)
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