Most of us have 23 pairs of chromosomes, half from each of the parents. Sometimes, cell division in the sperm and egg or during early embryonic development causes the occurrence of an extra pair of chromosomes in the genetic code of the fetus.

This condition of having an extra pair of chromosomes is known as aneuploidy. Aneuploidy affects development issues because chromosomes contain all the important information that regulates growth, development, and bodily functions. Extra chromosomes mean additional genetic material. This additional genetic material, in turn, disrupts the normal functioning of cells and interferes with critical biological processes.

For example, an extra pair of chromosome 21 causes Down syndrome, which can result in characteristic physical features, intellectual disabilities, and an increased risk of heart and digestive diseases.

Aneuploidy screening is a prenatal (before birth) test that assesses the risk of chromosomal abnormalities in a developing fetus, mainly extra (or sometimes, missing) chromosomes.

Many screening kits can test for a large variety of risks including cystic fibrosis, spinal muscular atrophy, sickle cell disease, thalassemia, Down syndrome, Edwards syndrome, Patau syndrome, and so on. But only a handful of them are 100% safe and reliable. A good aneuploidy screening test should be a non-invasive prenatal test that can evaluate any genetic risks safely and reliably.

What are Aneuploidies?

An aneuploidy means the occurrence of extra or missing chromosomes. This leads to an imbalance in the genetic code—Which is usually composed of 23 pairs of chromosomes.

This imbalance can disrupt bodily functions and lead to significant developmental challenges as well as health issues. Not all aneuploidies are equally severe.

Some aneuploidies, such as Down syndrome (trisomy 21), are more common and well-studied, while others may be rarer.

Trisomy 18 and trisomy 13, where there are three copies of chromosomes 18 and 13 respectively, are also common aneuploidies. Trisomy 18 is called Edwards syndrome and trisomy 13 is known as Patau syndrome.

Extra genetic material or the lack of genetic material introduced by an imbalance in chromosome count can negatively affect gene expression, protein production, and cellular communication. These can lead to widespread effects on various organ systems and developmental milestones.

The outcome isn’t so easy to determine. The specific genes affected and the individual variation in genetic makeup make the outcome different from one person to another. In fact, the severity of the growth issues can vary wildly and individuals might exhibit a range of abilities and challenges.

The risk of aneuploidy tends to increase with maternal age but age alone isn’t the only reason behind an aneuploidy. The exact reasons behind cell division errors such as nondisjunction, translocation, and mosaicism that lead to an abnormal number of chromosomes are not fully understood.

It’s suspected that everything from exposure to certain environmental factors to genetic predisposition can play a role in this.

Why is Aneuploidy Screening Important?

Aneuploidy screening is important for a variety of reasons—Early detection, additional information, and time to prepare being the most important ones.

• Early detection of syndromes with aneuploidy screening can allow for timely intervention and further diagnostic testing. You can also look into suitable counseling and emotional support.
• The screening provides information on the likelihood of specific abnormalities. This risk assessment can help parents and healthcare providers make better decisions regarding further diagnostic testing or treatments.
• You can’t know the full extent of the risks to make informed decisions if you don’t know about the possibility of an aneuploidy. Aneuploidy screening helps you discuss the options and potential outcomes so you can plan for the future accordingly.
• For individuals who receive a high-risk result indicating an increased chance of a chromosomal abnormality, aneuploidy screening allows them to emotionally and psychologically prepare for the potential challenges associated with having a child with special needs.
• Aneuploidy screening results can guide personalized prenatal care and management. If a high-risk result is obtained, it may lead to more frequent monitoring, specialized ultrasounds, or consultations with genetic specialists. This personalized care ensures that any potential complications or health issues are identified and addressed promptly.

How is it Performed?

There are two ways to perform aneuploidy screening—Non-invasive prenatal testing (NIPT) or invasive testing such as chorionic villus sampling (CVS) or amniocentesis.

NIPT works with a simple blood test from the pregnant individual. Upon analyzing the fetal DNA that’s circulating in the maternal bloodstream, this test can screen for common aneuploidies such as Down syndrome with high accuracy.

Invasive testing methods such as CVS and amniocentesis rely on obtaining samples from fetal tissues or fluids to analyze genetic information. In CVS, a small sample of villi is collected. Chorionic villi are finger-like projections on the placenta. In amniocentesis, a procedure usually performed between weeks 15 and 20 of pregnancy, a small amount of amniotic fluid is extracted from the uterus by needling through the abdomen.

Do I Need Aneuploidy Screening?

You’re recommended to undergo aneuploidy screening if:

• You’re 35 or above at the time of delivery;
• There’s a known family history of genetic disorders;
• There had been previous pregnancy complications;
• There were any abnormal findings on routine ultrasound examinations.

It’s always best to be on the safe side. The cost of non-invasive aneuploidy screening can range from $800 to $2000. Most tests are covered by insurance. If the pregnancy is considered high-risk for a genetic or chromosome condition, then it’s very likely the insurance will cover it. Many options are covered in low-risk pregnancies as well.

In Conclusion

Genetic testing or aneuploidy testing is important to assess the risk of chromosomal abnormalities like Down syndrome, Edwards syndrome, and Patau syndrome. Knowledge of such complications can help you make better decisions and plan ahead.