XXX syndrome, triple X syndrome

The XXX syndrome is also known as super female. It is a hereditary defect in which there are three sex chromosomes instead of two. In terms of appearance, we are dealing with a girl/woman, but there may be a number of external characteristics that are slightly different. Mental disadvantages can also arise. How do you recognize XXX syndrome and how common is it in girls?

X and Y chromosome

To explain what XXX syndrome is, first discuss what the X chromosome actually is. The X chromosome, but also the Y chromosome, are sex hormones. The egg cell always has an X chromosome. The sperm cell has either an X chromosome or a Y chromosome. The final gender of the future baby is therefore determined by the type of sperm cell. After fertilization between egg cell and sperm cell, it looks like this:

  • Egg cell + X chromosome sperm cell = XX = girl
  • Egg cell + Y chromosome sperm cell = XY = boy

A girl therefore contains two sex chromosomes: XX. This is also called a chromosome pair. Every human has 46 chromosomes, divided into 23 pairs, of which only one pair is the sex chromosome pair. With abnormalities, more or fewer chromosomes may be present.

XXX syndrome

: super female, triple X syndrome, 47XXX syndrome, trisomy
So there is one too many X chromosomes. It is more common for an egg or sperm cell to have one too many X chromosomes. Older women (over 30 years old) in particular are more likely to experience this. When an egg cell with the XX chromosome fuses with an X sperm cell, an XXX baby is created. On average, XXX syndrome occurs in 1 in 1,000 girls. This means that there are between 8,000 and 8,500 girls/women in the Netherlands with XXX syndrome. Because this abnormality does not show any obvious characteristics, it very often goes unnoticed. This can only come to light if prenatal examination is carried out during pregnancy. Prenatal testing is often performed due to the age of the mother or a hereditary defect.
In some girls there is a normal 46.XX pattern and there is also a 47.XXX pattern as a mosaic. This means that XXX is found in part of the body’s cells. This is the result of an error during cell division and occurs in 1 in 5 girls who suffer from XXX syndrome.


At birth, the birth weight may be lower than normal. Yet this difference is so small that it is often not even noticeable or there is no reason to worry. During the first three months you may notice that the baby is less able to lift her head compared to other babies. The neck muscles appear weaker. Muscle tension is sometimes reduced. Upon inspection it is noticeable that the head size lags somewhat behind in growth. During toddlerhood, it is noticeable that the girl is somewhat longer in height than her peers. By puberty the difference in height has decreased again.
In general, most girls with XXX syndrome will show developmental delays. Crawling, standing and walking happen a little later than usual. Language development also starts later. Some girls receive speech therapy and/or physiotherapy. Yet most girls develop completely normally, despite the delay. In some cases there remains a backlog that can no longer be made up. Sometimes the girl remains stiff or stiff in her movements and is labeled as clumsy. However, the girl may appear very overactive because she has difficulty sitting still. It is often diagnosed as ADHD.
In terms of intelligence, many girls develop normally and follow regular education. The IQ may lag behind some people. A number of girls attend special (primary) education. Rarely does a serious mental disorder develop. Dyslexia is more common in these girls, as are Non-verbal Learning Disabilities. Emotionally, these girls can seem insecure and sometimes even anxious. Sometimes there is little self-confidence.
There are few external features. If they are present, this is so minimal that it is not associated with XXX syndrome. For example, the teeth may be less developed. Many girls therefore have to wear braces. The eyes may be a little further apart than normal. A curvature of the fingers, especially the little finger, is more common than usual.
The above symptoms and characteristics do not always occur simultaneously. Often there is one or more characteristics that are so minimal that the XXX syndrome is not suspected. This often makes the diagnosis difficult.


When the syndrome has been diagnosed through chromosome research, this does not mean that the abnormality can be cured. It is simply not possible to remove the extra chromosome. If it is discovered during pregnancy, this is often not a reason for abortion: most girls develop normally or have a slight delay. The abnormalities that arise can often be easily treated. Speech therapy and physiotherapy during her early years can often help the girl on her way. In addition, psychological help is sometimes needed to remove the girl’s insecurity and fears. The future of most girls looks quite normal compared to other girls. Rarely does XXX syndrome lead to such serious mental retardations that the girl needs extra guidance.

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