Health Mommy Thoughts

The Scariest Word You’ve Never Heard: Trisomy

Outside of those who have a child with a genetic defect, or those who have had prenatal DNA testing, the word “trisomy” doesn’t strike fear in the hearts of many women, but what you don’t know, can indeed hurt you – or, in this case – your unborn child. Nearly twenty percent of all infant mortality cases are due to birth defects, and today we’ll learn about three of the most common.

An estimated 120,000 children are born in the United States each year with a birth defect (about 1 in every 33 births). Genetic conditions are currently responsible for three to four percent of these defects, with chromosomal abnormalities, such as the three we’ll talk about today comprising about one percent of total births. However, this number rises with certain risk factors, such as age.


Three of these genetic defects are the topic of today’s post, Trisomy 21, Trisomy 18 and Trisomy 13. The most common of the three, Trisomy 21 appears in 1 in every 800 newborns. While the other two are more rare, the number of children born with these genetic conditions aren’t decreasing. In fact, the percentage of births with genetic defects has stayed relatively stagnant since these sorts of birthing stats started being documented.

What are Trisomies?

Healthy babies are born with 23 pairs of chromosomes. Babies with genetic defects are typically born with an additional copy of one of these pairs. These instances of chromosomal abnormalities are known as trisomies. A trisomy is simply a genetic defect brought on by chromosomal abnormalities.

What is Trisomy 21?

Trisomy 21 (Down syndrome) is a condition in which the child is born with a copy of a specific set of chromosomes. This defect leads to children born with intellectual disability, as well as a characteristic facial appearance and a condition known as hypotonia (weak muscle tone) in infancy. The overall intellectual disability is typically mild to moderate, and individuals affected are often quite high functioning although there are obvious cognitive impairments to contend with. In addition, they may experience a variety of birth defects such as heart defects, and digestive abnormalities but are often relatively healthy. The affected go on to live relatively long lives, with an average lifespan of about 56 years, as opposed to the much shorter lifespan of those affected with other trisomies.

What is Trisomy 18?

Trisomy 18 (Edwards syndrome) is typically caused by the individual having three copies of the 18th chromosome instead of the normal two copies. This extra material disrupts normal development and causes slow growth before birth, referred to as intrauterine growth retardation, as well as low birth weight. Trisomy 18 often results in a number of medical problems, and those affected often die before birth, or within their first month of life. Only five to 10-percent of individuals with Trisomy 18 survive past the first year of life, and those that do are often affected with severe intellectual disability requiring around the clock medical care.

What is Trisomy 13?

Trisomy 13 (Patau syndrome) is a genetic condition caused by a child being born with three copies of the 13th chromosome. This condition often leads to small and poorly developed eyes (micropthalmia), extra fingers or toes, weak muscle tone (hypotonia), cleft lip or pallet, and brain or spinal cord abnormalities as well as heart and lung defects. Due to these severe medical issues, those with Trisomy 13 rarely survive their first few weeks of life, and much like Trisomy 18, only five to 10 percent live past their first year.

What Can I Do About It?

While there are risk factors associated with genetic defects, there remains no concrete evidence as to any single cause. Advanced age (35 years and older) is one of the most commonly cited reasons for genetic defects, and there is evidence to back up the argument that older mothers are more likely to have children with genetic defects, the defects still occur in younger mothers as well.

Testing for these genetic abnormalities is available through your physician as early as week 10 in your pregnancy. If your healthcare professional deems you to have increased risk criteria, such as advanced age or a family history of genetic defects, a positive serum test and ultrasound finding, they will often order prenatal DNA testing. This test requires just a small amount of blood that your doctor will send to a lab and your healthcare professional will have the results back in about five days after the lab receives the sample. If the test comes back positive for signs of any of these three trisomies, additional tests may be ordered.

While there isn’t a conclusive cause, you can increase the odds of having a healthy child by reducing risk factors such as having children earlier in life, avoiding alcohol and tobacco, and avoiding foods high in mercury or other contaminants. In addition, a healthy prenatal environment that features a reduced level of stress, healthy diet, and exercise are all proven to be key contributors to a healthy pregnancy and delivery.

Even the healthiest of lifestyles and a lack of all risk factors can produce a child with genetic defects, but you can certainly do your part by minimizing risk factors when attempting to conceive and after conception.

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