Sex chromosome conditions in the foetus

Diagnosis and treatment

With sex chromosome abnormalities, it is currently unclear in how many cases the diagnosis can be confirmed by performing an amniocentesis. In this case, there is a real chance that the baby does not have a sex chromosome abnormality. Only an amniocentesis provides 100% certainty. There is also a chance that a diagnosis of a sex chromosome condition could be missed by NIPT. We don't know exactly how likely that is.

When you request NIPT, you must make a few choices. The third choice you will have to make on the consent form is whether you want to be informed of an increased risk of a sex chromosome disorder.

This primarily includes:

Girls with Turner's Syndrome
Girls with Triple X Syndrome
Boys with Klinefelter's Syndrome

There can also be other, even rarer sex chromosome conditions. The chance is roughly 1 out of 400, though we do not have an exact percentage.

Girls with Turner's Syndrome

How often is this abnormality found?

In 1 out of every 2,000 newborn girls.

What is the possible impact on your baby's health?

Most girls born with Turner's Syndrome appear normal at birth.
As a child, their growth slows by more than 95% and they are very small in stature. This is often the time when the diagnosis is made, usually during the toddler years. Growth hormone is an option in this case.
Common medical problems include recurrent ear infections, possibly with impaired hearing, the need for glasses or braces and increased blood pressure. There is also an increased chance of poor development of the aortic arch (up to 50%). An operation is sometimes necessary.
There is delayed puberty development. Menstruation does not occur because there is a loss of ovarian function.
There is almost always a question of infertility or severely reduced fertility. If a woman wishes to have children, there are alternatives (e.g. egg cell donation).
The intelligence (IQ) of girls with Turner's Syndrome is normal and comparable with any brothers and sisters from the same family.
With a good education and support, any potential issues may be dealt with or helped.

What is the life expectancy?

Turner's Syndrome is sometimes detected after the 12-week ultrasound, when there is a (often severely) thickened nuchal fold, by
performing a chorionic villus sampling or amniocentesis. The foetus usually dies during pregnancy or the pregnancy is ended.
If there is a normal nuchal fold, and if there are no heart defects, life expectancy is normal.

How can you test for this condition?

12-week ultrasound:
- In the case of a thickened nuchal fold: NIPT is not performed. Either chorionic villus sampling or an amniocentesis is indicated.
- For a normal nuchal fold: testing using NIPT
Does the NIPT show an increased risk for this syndrome? In that case, an amniocentesis is necessary to either confirm the NIPT result or to rule out the condition. You may, if you wish, also wait until the birth of your baby to confirm the diagnosis.

Do you need to explicitly select this test on the informed consent form?

Yes, if you would like to test for this syndrome, you must explicitly indicate this on the informed consent form. In that case, you also test automatically for the other sex chromosome conditions. It is not possible to test for this condition only.

What if you want to end the pregnancy?

The ethical committee will be required to meet.

More information?

www.turnerkontakt.be and www.turnercontact.nl

Girls with Triple X Syndrome

How often is this abnormality found?

In 1 out of every 1000 births of girls in Belgium, often without symptoms.

What is the possible impact on your baby's health?

Girls with Triple X Syndrome usually appear completely normal.
There are no typical health problems.
Fertility is also often normal.
Intelligence (IQ) is generally ten points lower than any brothers and sisters from the same family.
There is a possibility for mild problems with learning and speaking, and there can be a somewhat slower development of motor skills. With proper support, this can be dealt with well.
Often, the diagnosis is never made.

What is the life expectancy?

Normal

How can you test for this condition?

Detection on the 12-week ultrasound is not possible: There is no thickened nuchal fold associated with Triple X Syndrome.
Triple X can be detected with NIPT.
Does the NIPT show an increased risk for this syndrome? In that case, an amniocentesis is necessary to either confirm the NIPT result or to rule out the condition. You may, if you wish, also wait until the birth of your baby to confirm the diagnosis.

Do you need to select this text explicitly on the informed consent?

Yes, if you would like to test for this syndrome, you must explicitly indicate this on the informed consent form. In this case, you also test automatically for other sex chromosome conditions. It is not possible to test for this condition only.

What if you want to end the pregnancy?

The ethical committee will be required to meet.

More information?

www.triple-x-syndroom.nl and www.kinderneurologie.eu

Boys with Klinefelter's Syndrome

How often is this abnormality found?

In 1 out of every 500 births of boys in Belgium.

What is the possible impact on your baby's health?

Boys with Klinefelter's Syndrome usually appear completely normal.
The intelligence (IQ) of boys with Klinefelter's Syndrome is generally ten points lower than any brothers and sisters from the same family.
There is a possibility for mild problems with learning and speaking. There can also be a somewhat slower development of motor skills. With good support, this can be dealt with well.
There is a slightly increased risk of developing a psychiatric condition.
Sperm cells break apart in the ejaculate, and so these men are generally infertile.
The diagnosis is often only made during adulthood, when there is an indication of reduced fertility.
If a man wishes to have children, there are alternatives (e.g. donor sperm).

What is the life expectancy?

Normal

How can you test for this condition?

Detection on the 12-week ultrasound is not possible: There is no thickened nuchal fold associated with Klinefelter's Syndrome.
Klinefelter's Syndrome can be detected using NIPT.
Does the NIPT show an increased risk for this syndrome? In that case, an amniocentesis is necessary to either confirm the NIPT result or to rule out the condition. You may, if you wish, also wait until the birth of your baby to confirm the diagnosis.

Do you need to explicitly select this test on the informed consent form?

What if you want to end the pregnancy?

The ethical committee will be required to meet.

More information?

www.klinefelter.be and www.klinefelter.nl

What if NIPT indicates a sex chromosome condition?

If NIPT shows an increased risk of a sex chromosome condition, that does not make it a certain diagnosis. Only an amniocentesis can give you 100% certainty. The chance of a false positive result is significantly larger than that for Down's Syndrome, and is most likely when screening for Turner's Syndrome. Your pregnancy will be at the approximately 16 week mark.
You are not obliged to have amniocentesis performed. You may, if you wish, also wait until the birth of your baby in order to confirm the diagnosis. This would be done by performing a blood test on the baby.
If a sex chromosome abnormality is confirmed (either during the pregnancy or at birth), you will be given extensive information about the abnormality by a specialised paediatrician.
Sometimes, a sex chromosome condition is suspected during childhood or puberty. Your paediatrician will definitely speak to you about it. A blood test may be performed during childhood or puberty to confirm the diagnosis.
A normal life is completely possible when there is a sex chromosome condition. The diagnosis may be made during puberty, and it may be made in adulthood (usually when there are problems with fertility). Sometimes, a diagnosis is never made.

We will listen to your questions and wishes, and then discuss them as a team with physicians and midwives.

Continuing the pregnancy after a diagnosis

Some diagnoses can be useful information for when you are raising your child. It can also pull the wool from your eyes, and you may not be completely happy with the information you receive, leading you to think afterwards that you would have been better off not knowing.

Would you like to continue the pregnancy? Then it is very difficult to estimate what influence 'knowing' will have on the continuation of the pregnancy. Given that the detection of these syndromes is still so recent, there is very little research about this.

Will 'knowing' cause anxiety during the rest of the pregnancy? The anxiety may be so great that you end up deciding to end the pregnancy. It can be difficult to process all of this.
How will you feel as you raise your child? Will the diagnosis keep haunting you? Will it cause stress? Will you view your child 'differently'?
When should you tell your child about the diagnosis?
- During childhood, if your daughter with Turner's Syndrome is small in stature? Or during puberty, if menstruation does not start?
- If your daughter has Triple X Syndrome, there are often no or few symptoms. Fertility is also often normal.
- If my son has Klinefelter's Syndrome, when should I tell him? When he is 18 years old? Later? Or when my son is in a relationship? If he has children? We estimate a fairly high likelihood of this diagnosis having a negative impact on the self-image of a young adult son or on the formation of a normal relationship. But there is no good research on this topic.
- What do we know? Klinefelter's Syndrome is one of the many causes of male infertility problems. Adult men who wish to have children in a stable relationship can usually cope with the diagnosis of fertility issues, particularly because there are many treatment options.

Ending the pregnancy after a diagnosis

This tends to be more the exception than the rule when there are sex chromosome conditions:

Ending a pregnancy for Triple X or Klinefelter's Syndrome is not allowed in many Flemish hospitals, which is also the case in our hospital.
For Turner's Syndrome, abnormalities sometimes show on an ultrasound. In which case, the necessary specialists will be consulted, along with the hospital's ethical committee.

For a sex chromosome condition, you should keep in mind that you may be referred to a foreign institution (in the Netherlands or England, for example).

Every care provider (physician or midwife) has the right to refuse to end a pregnancy if the decision to do so does not agree with his/her ethical point of view. In this case, however, there is an obligation to refer you to another centre where you would be able to end the pregnancy.

Treatment centres and specialisations

Ghent - Pregnancy and childbirth

Obstetrics and maternity

Latest publication date: 23/12/2024

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