Types of Chromosome Abnormalities

Your baby’s growth and development starts sooner than you might think. When you and your partner’s genes come together during pregnancy, it means more than just guessing whether your child will have their dad’s smile or their mom’s eyes: it could mean a risk for genetic problems and, in some cases, chromosome abnormalities. Genetic problems can happen when your baby is so small you might not even know they’re there, but trained perinatologists like the ones at Valley are experts in knowing what to look for.

Chromosomes and Genes

A gene is a set of instructions for how a person grows and develops throughout their lives. There are thousands of these genes in the human body, and they are contained in strands of genetic material called chromosomes. There are 46 total chromosomes in normal cells, divided into 23 pairs. During fertilization, 22 chromosomes plus one X chromosome from the mother’s egg and 22 chromosomes plus either an X or Y chromosome from the father’s sperm combine to form the 46 chromosomes that make up the very first cell that will become a baby. Problems in certain genes or the chromosomes can cause health complications, including miscarriage, stillbirth, birth defects, and some disabilities.

Are Chromosome and Gene Disorders the Same?

Chromosomes contain genes, but that doesn’t mean that chromosome and genetic disorders are the same thing. A person can have the right number of chromosomes that have the correct structure, but certain mutations in certain genes can still cause a health condition or disease. At the same time, all of the genes on the chromosomes can be normal, but because of the altered structure or number of chromosomes, the genes might not work properly. It can be tough to distinguish, but a genetic counselor or another specialist can talk to you about the difference in more detail based on your unique case.

Types of Chromosome Abnormalities

Abnormalities that affect the number or structure of chromosomes come in many forms. Some abnormalities happen during the combining of sex cells that make up a baby or during the division of cells as they grow.

  • Monosomy: A chromosome is missing
  • Trisomy: There is an extra chromosome
  • Deletion: Part of a chromosome is missing
  • Duplication: Part of a chromosome was duplicated
  • Translocation: A portion of one chromosome is transferred to another chromosome
  • Inversion: Part of a chromosome was broken off, turned around, and reattached
  • Ring: A chromosome was broken off and formed a circle or ring instead of a strand
  • Mosaicism: Two or more sets of chromosomes with different genetic material exist

Risk Factors for Chromosome Abnormalities

Changes in chromosome numbers are random events during cell division, and as a result, most chromosome abnormalities can’t be inherited. There are some factors that put a mother at risk for delivering a baby with a chromosome abnormality. Your genetic counselor or healthcare provider will be able to tell you more about your specific risk factors.

In general, older mothers have a higher chance of having a baby with a chromosomal condition. This is because her eggs are the same age as she is, and chromosome errors are more likely to result from the aging process. The risk is greatest for women who are 35 years or older. Mothers who have had previous pregnancies affected by chromosome abnormalities also have a higher chance of having their current or future pregnancy affected.

Family history plays a role in chromosome abnormalities as well. If you, your partner, or someone in either of your families has a chromosome condition, your baby could have a higher chance of developing one as they develop. A genetic counselor is trained in which conditions run in families and can help you understand your risk.

Testing Options

There is no treatment for genetic abnormalities. There is, however, a lot of value in getting testing done to learn about your baby’s potential risk for chromosome abnormalities. Knowledge can do a lot for a family, and perinatologists and other high-risk pregnancy experts like the ones at Valley have a variety of ways to keep parents informed about what could lead to health problems.

Genetic Counseling

Counseling is a good first step for a young family to take prior to any further testing. A genetic counselor will help you figure out what anomalies your baby might be at risk for based on factors in your family and will be able to help make information about those anomalies clear to you. They are experts in inheritance patterns and other risk factors that could lead to early detection and even treatment of some problems. When combined with other testing, this counseling could give a mother-to-be peace of mind.


If you have a high-risk for genetic disorders, whether because of a family history, a previous child born with a chromosomal anomaly, age, or abnormal ultrasound results, you might opt to get an amniocentesis test. This test takes a small amount of amniotic fluid from the sac surrounding your baby in the womb, and this fluid gets sent to a lab for analysis. The fluid contains fetal cells that can be tested for birth defects connected to chromosomal abnormalities, such as Down syndrome, or neural tube defects.

Chorionic Villus Sampling

Chorionic Villus Sampling is another test that collects samples of genetic material around your baby for lab testing. The difference is where this material comes from. This test takes cells from the placenta where it’s attached to the uterine wall, either through the cervix or abdominal wall. These cells, called chorionic villi, are placental tissue that share the fetus’ genetic makeup, which helps to detect chromosome abnormalities.

Genetic Testing and Perinatal Care at Valley

Every mother worries about how healthy her baby will be during her pregnancy and delivery. Mothers in high-risk pregnancy situations are no exception, and it’s so important to know as much as possible about your baby’s health. For Phoenix-area mothers-to-be and their pregnancy care teams, Valley has the resources and specialized training to provide peace of mind and more information about potential chromosomal abnormalities. Whether a mother is seeking genetic counseling, prenatal screening, or diagnostic tests for chromosome abnormalities, Valley’s team can help her care team make informed choices about her baby’s health as well as hers. Talk with your Ob/Gyn about co-managing your pregnancy with Valley. Call 480.756.6000 or contact us online.