Trisomy 21, also called Down syndrome, is a condition in which a baby is born with an extra chromosome. Chromosomes are small "packages" of genes in the body. Genes are pieces of code passed down from parents to children. They make us who we are.

Chromosomes determine how a fetus forms during pregnancy, functions as it grows in the womb, and after birth. Typically, a baby is born with 46 chromosomes. Babies with Down syndrome have an extra copy of one of these chromosomes, chromosome 21. A medical term for having an extra copy of a chromosome is “trisomy.” This extra copy changes how the fetus’s body and brain develop, which can cause both mental and physical challenges for the baby.

Even though people with Down syndrome might act and look similar, each person has different abilities. People with Down syndrome usually have an IQ (a measure of intelligence) in the mildly-to-moderately low range and are slower to speak than other children.

Down syndrome can affect babies born to women of any age. However, as women get older, the chances increase for having a baby with Down syndrome.

Content provided by the Centers for Disease Control and Prevention (CDC) and GDSP. For information and references about trisomy 21, please visit: Facts about Down Syndrome

Recommended Resources

• Understanding a Down Syndrome Diagnosis
• Down Syndrome Pregnancy
• Genetics Home Reference

Parent Support Groups

• National Down Syndrome Society
  
• National Down Syndrome Congress
  
• Down Syndrome Diagnosis Network

Data Sheet

• Birth Defects Monitoring Program Data Sheet on Trisomy 21
  

Trisomy 13 is a condition in which a person has an extra chromosome. Chromosomes are small "packages" of genes in the body. Genes are pieces of code passed down from parents to children. They make us who we are.

Chromosomes determine how a fetus forms during pregnancy and how the baby's body functions as it grows in the womb and after birth.

Typically, a baby is born with 46 chromosomes. Babies with trisomy 13 syndrome have an extra copy of one of these chromosomes, chromosome 13. A medical term for having an extra copy of a chromosome is 'trisomy.'

Trisomy 13 syndrome is a rare chromosomal disorder in which all or a large portion of chromosome 13 is present three times, (trisomy), rather than twice in each cell of the body.

This extra copy changes how the baby's body and brain develop, which can cause distinctive physical features, structural birth defects and developmental disabilities.  Most babies with Trisomy 13 are lost through miscarriage.

Chromosome abnormalities are usually present at conception, the result of errors in egg or sperm formation. In rare cases chromosome abnormalities are inherited. The majority of babies born with trisomy 13 are female. Trisomy 13 can be diagnosed prenatally by amniocentesis or chorionic villus sampling. Trisomy 13 can affect babies born to women of any age. However, as women get older, the chances increase for having a baby with trisomy 13.

Recommended Resources

• Genetics Home Reference (Trisomy 18)
• Genetics Home Reference (Trisomy 13)
  

Parent Support Groups

• Trisomy 18 Foundation
• Chromosome 18 Registry & Research Society
• Support Organization for Trisomy 18, 13 and Related Disorders (SOFT)

Data Sheet

• Birth Defects Monitoring Program Data Sheet on Trisomy 13 

Trisomy 18 is a condition in which a person has an extra chromosome. Chromosomes are small "packages" of genes in the body. Genes are pieces of code passed down from parents to children. They make us who we are.

Chromosomes determine how a fetus forms during pregnancy, functions as it grows in the womb, and after birth. Typically, a baby is born with 46 chromosomes. Babies with trisomy 18 syndrome have an extra copy of one of these chromosomes, chromosome 18. A medical term for having an extra copy of a chromosome is “trisomy.”

Trisomy 18 syndrome is a rare chromosomal disorder in which all or a large portion of chromosome 18 is present three times (trisomy), rather than twice in each cell of the body. This extra copy changes how the fetus’s body and brain develop, which can cause distinctive physical features, structural birth defects and developmental disabilities. Most babies with trisomy 18 are lost through miscarriage.

Chromosome abnormalities are usually present at conception, the result of errors in egg or sperm formation. In rare cases chromosome, abnormalities are inherited. The majority of babies born with trisomy 18 are female. Trisomy 18 syndrome can be diagnosed prenatally by amniocentesis, or chorionic villus sampling.

Trisomy 18 can affect babies born to women of any age. However, as women get older, the chances increase for having a baby with trisomy 18.

Recommended Resources:

• Genetics Home Reference (Trisomy 18)
  
• Genetics Home Reference (Trisomy 13)

Parent Support Groups

• Trisomy 18 Foundation
• Chromosome 18 Registry & Research Society
• Support Organization for Trisomy 18, 13 and Related Disorders (SOFT)

Data Sheet

• Birth Defects Monitoring Program Data Sheet on Trisomy 18 

As a fetus is forming, the neural tube extends from the top of the head to the end of the spine. This develops into the baby's brain and spinal cord. The neural tube is completely formed by 5 weeks after conception.

When there is a problem with the neural tube, it is called a neural tube defect. Two types of neural tube defects are spina bifida and anencephaly. When there is an opening in the spine, it is called spina bifida. This defect often causes paralysis of the baby's legs. It may also cause loss of bowel and bladder control. Anencephaly occurs when most of the brain does not develop. This defect causes the death of the baby or newborn.

For information and references about neural tube defects, please visit: Facts about Neural Tube Defects, What is Spina Bifida? and Facts about Encephalocele.

​Recommended Resources

• Expectant Parents Guide to Spina Bifida
  
• Genetics Home Reference

Parent Support Groups

• Spina Bifida Association
  

Data Sheet

• Birth Defects Monitoring Program Data Sheet on Neural Tube Defects​

Turner syndrome is a genetic condition that can cause mild developmental delays, learning disabilities, heart defects, and infertility. The signs of Turner syndrome are different from one person to another. Some people have no obvious signs. Some pregnancies affected by Turner syndrome can have serious results. For example, miscarriages are more common in pregnancies carrying a fetus with Turner syndrome. 

Turner syndrome occurs when there is only one X chromosome. Most people either have two X chromosomes (XX) or one X and one Y chromosome (XY). Your provider might refer to these as “sex chromos​omes.” Chromosomes help the fetus develop and are found in nearly every cell in the body.

Recommended resources for X and Y chromosome variations

• eXtraordinarY Kids Program Resources
• Lettercase National Center for Prenatal and Postnatal Resources - This website provides a library of resources for patients receiving a prenatal diagnosis with all materials reviewed by representatives of the national medical, genetics, and advocacy organizations.
• HealthyChildren.org by AAP - This parenting website provides information about different conditions for patients in understandable language​​ 

Klinefelter syndrome, also called ​XXY, can cause mild developmental delays, learning disabilities, and infertility. The signs of Klinefelter syndrome are different from one person to another. Some people have no obvious signs. 

Klinefelter syndrome occurs when there is an extra X chromosome (XXY). Most people either have two X chromosomes (XX) or one X and one Y chromosome (XY). Your provider might refer to these as “sex chromosomes.” Chromosomes help the fetus develop and are found in nearly every cell in the body.​​

Recommended resources for X and Y chromosome variations

• eXtraordinarY Kids Program Resources
• Lettercase National Center for Prenatal and Postnatal Resources - This website provides a library of resources for patients receiving a prenatal diagnosis with all materials reviewed by representatives of the national medical, genetics, and advocacy organizations.
• HealthyChildren.org by AAP - This parenting website provides information about different conditions for patients in understandable language​​ 
  

Trisomy X can cause mild developmental delays and learning disabilities. The signs of trisomy X are different fr​om one person to another. Some people have no obvious signs. 

Trisomy X occurs when there is an extra X chromosome (XXX). Most people either have two X chromosomes (XX) or one X and one Y chromosome (XY). Your provider might refer to these as “sex chromosomes.” Chromosomes help the fetus develop and are found in nearly every cell in the body.​​

Recommended resources for X and Y chromosome variations

• eXtraordinarY Kids Program Resources
• Lettercase National Center for Prenatal and Postnatal Resources - This website provides a library of resources for patients receiving a prenatal diagnosis with all materials reviewed by representatives of the national medical, genetics, and advocacy organizations.
• HealthyChildren.org by AAP - This parenting website provides information about different conditions for patients in understandable language​​
  

XYY can cause mild developmen​​tal delays and learning disabilities. The signs can vary from person to person. Some people have no obvious signs.

XYY is caused when there is an extra Y chromosome. Most people either have two X chromosomes (XX) or one X and one Y chromosome (XY). Your provider might refer to these as “sex chromosomes.” Chromosomes help the fetus develop and are found in nearly every cell in the body.​​

Recommended resources for X and Y chromosome variations

• eXtraordinarY Kids Program Resources
• Lettercase National Center for Prenatal and Postnatal Resources - This website provides a library of resources for patients receiving a prenatal diagnosis with all materials reviewed by representatives of the national medical, genetics, and advocacy organizations.
• HealthyChildren.org by AAP - This parenting website provides information about different conditions for patients in understandable language​​​