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Height Difference in Twins

A case study by iHeal HealthTech on several twins around India

There are two types of twins, such as #IdenticalTwins and #Non-Identical Twins.

Identical twins are a result from a single fertilized egg splitting into two separate embryos. On the other hand, non-identical twins are more common and occur when two separate eggs are fertilized by two different sperm cells. One-third of all twins are identical twins.

It's fascinating to think about how genetics play a role in height differences between twins. According to research, #GeneticFactors account for 60-80% of the variability in height differences between individuals. Environmental factors such as Nutrition also play a role, accounting for the remaining 20-40%.

Identical twins share identical genetic information and are of the same sex, whereas non-identical twins only share half of their genetic information and can be of different sexes. Due to this, the height variation between identical twins is normally very less and it could vary significantly in non-identical twins. In Japan, there are non-identical twin sisters who are 75 cm apart.

Case Study of height differences in Identical Twins:

Let us consider the case study of Sita and Gita (name changed due to privacy). Considering Sita and Gita as identical twins, let us analyse the various major factors which could lead to height differences between identical twins.


Interestingly, even identical twins, who share the same DNA sequence, can have differences in the way their DNA is folded. This can lead to variations in gene expression and ultimately contribute to differences in their physical characteristics and health outcomes. Therefore, while identical twins share a lot in common genetically, the way their DNA is folded can have important implications for their individual traits and health.

Effects of Epigenetics:

Epigenetics is an area of study that focuses on how our genes interact with our environment and behavior to shape our physical and mental traits. One intriguing example of this phenomenon is the impact of epigenetics on height development in twins. Despite sharing identical genes, twins can differ in height due to differences in their exposure to environmental factors. For instance, if one twin is exposed to more trauma or stress in their early years, their growth and development may be impacted, resulting in a difference in height between the two.

Connection to the placenta:

The differences in #nutrition between twins can also depend on their connection to the placenta. This can ultimately impact their #height and overall growth and development.

During pregnancy, each twin is connected to the placenta of their mother. However, the level of connection can vary, with one twin being more connected than the other. The twin well connected to the placenta typically receives more #nutrition, which positively impacts its growth and development.

Studies have shown that there is a significant difference in five amino acids between the two foetuses from the placenta, highlighting the importance of this connection. Even identical twins can receive different amounts of blood and nutrients in the womb, depending on their placement within the placenta.

The transport of oxygen from the placenta to twins can impact their growth and development, particularly in the brain and liver. Research has shown that if one twin experiences slower transport of oxygen from the placenta, they may end up with a smaller brain and liver size than their twin. This is because the brain and liver require a steady supply of oxygen to develop properly, and any disruption in the delivery of oxygen can have a negative impact.

Image source:

These images, which were taken from fetal MRI, depict the placental position in an easy way. Image A shows babies within the placenta. Image B shows their positions without the placenta. It could be seen that, Baby B who has received oxygen slowly, has small liver and brain when compared to Baby A.

Infections during childhood:

Research has shown that if one twin has developed infections two or three times during their childhood, they may end up shorter than their twin. This is because infections can have a negative impact on growth, particularly during the crucial developmental years of childhood. If a child is frequently sick, their body may divert energy away from growth and towards fighting off infections, which can ultimately lead to stunted growth.

So, in addition to genetics and environmental factors like nutrition, it's essential to consider a child's overall health when it comes to their height.

Nutrition changes:

One important factor to consider is nutrition. The food consumption of each twin plays a major role in their growth. While genetics play a significant role in determining height, how the body reacts to food we consume also has an impact. Recent research has shown that the way food affects identical twins can vary, with each twin carrying only 37% of identical #GutMicrobes when compared to 35% between any two unrelated persons.

Interestingly, the response to food can also differ between identical twins. For example, the spike in insulin and triglycerides after eating the same food can vary between twins, even though they share the same genetic information.

Key takeaways:

In conclusion, we can see that nutrition and environment are the major factors that can cause height differences between identical twins, apart from placental placement.
To promote healthy growth and development in twins, it's essential to ensure that they receive a nutritionally rich diet and are exposed to a happy and positive environment.
In addition, it's important to take proper care in the case of any childhood infections and prevent them from recurring.

By addressing these factors, parents of twins can help to minimize any differences in height between their children and promote optimal growth and development for both twins.



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