Feeling anxious about the future of a child with intellectual disabilities is completely natural as a parent.
How common are these intellectual disabilities?
Detailed information about intellectual disabilities is provided on this page, but to conclude, not all intellectual disabilities can be tested for with NIPT.
This is because intellectual disabilities more often occur independently of genetics. However, it is a natural thought to want to rule out that possibility as much as possible before birth.
Is it possible to detect intellectual disabilities using the three types of NIPT (chromosome 13, 18, and 21 testing) performed at most facilities?
Only the chromosome 21 test (Down syndrome test) targets intellectual disability. For trisomy 13 and 18, the physical disabilities are too severe, making it difficult to even recognize the intellectual disability. In other words, the condition is so severe that they often pass away early, making it impossible to even know if there is an intellectual disability.
However, isn’t the parents’ biggest worry that the child grows physically but continues to live with an intellectual disability?
If this can be known before birth, it is a parent’s heart to want to detect as many conditions as possible. Now, let’s consider in what cases intellectual disabilities might occur.
In the case of trisomy 13 and 18 mentioned earlier, the reason intellectual disability (as a standalone symptom) doesn’t just present itself is that these chromosomes carry far too many critical genes, so cases where it is *only* an intellectual disability are rare. Since they carry many genes related to life, it becomes difficult to sustain life before intellectual disability even becomes the primary concern. Now, what happens if there is an abnormality in the number or sequence of *some* genes? In many cases, life can be sustained, but it is often accompanied by impairment of the highly functional brain, causing intellectual disability.
NIPT is basically a test that examines the amount of chromosomes. Since it cannot check for chromosomal sequence abnormalities, what NIPT can test for is strictly the partial changes in the amount of chromosomes. The most common genetic abnormalities are those of amount rather than sequence. Therefore, NIPT is very useful because it can investigate these abnormalities in amount.
So, how can we test for such intellectual disabilities?
First, those who view this website will likely notice that there are multiple options for NIPT. It means that there are tests other than those for chromosomes 13, 18, and 21 typically recommended by obstetricians. These “other tests” are widely performed around the world. Particularly well-known are sex chromosome abnormalities. Also, microdeletion and duplication syndromes involving parts of chromosomes are well-known conditions. This is because DiGeorge syndrome, which is included in this category, is said to be the second most common intellectual disability. It is the most common intellectual disability after Down syndrome. The average lifespan is said to be around 50 years. As I mentioned earlier, if only a part of a chromosome is missing, it is possible to sustain life, so with modern medicine, they may have a lifespan stretching into their 50s or 60s. However, their intelligence is typically around an IQ of 50, which makes it very difficult to live independently. Furthermore, sex chromosome abnormalities are accompanied by infertility and growth disorders in the child. By knowing this early, growth disorders can be prevented, and by the individual knowing they have a high probability of infertility, it becomes possible to receive advanced medical care such as TESE. Regarding sex chromosome abnormalities, while they may not be severe enough to be called intellectual disabilities, they are generally accompanied by learning disabilities. For more detailed information on these, please refer to the respective pages.
What I want to emphasize here is that NIPT is not limited to just three types; a variety of tests are now available, and many of them can early detect conditions accompanied by intellectual and developmental disabilities for which there is completely no cure. I harbor a certain amount of anxiety that NIPT is gradually spreading without these facts being fully communicated to pregnant women.
This is explained in detail on this website, so please take a look. If it is difficult to understand through text alone, we provide daily videos on YouTube. Please refer to those as well.