Trisomy 13 and trisomy 18 are
genetic disorders. They include a combination of birth defects. This includes severe
learning problems and health problems that affect nearly every organ in the body.
Most babies born with trisomy 13 or
18 die by age 1. But some babies with these disorders do survive the first year of
It’s hard to predict how long a child with these disorders might live. There are a
reports of babies with trisomy 13 or 18 surviving to their teens. But this is rare.
Chromosomes come in sets of 2, or pairs. Most people have 23 pairs of chromosomes
in their cells. Trisomy means that a person has 3 of a certain chromosome instead
of 2. Trisomy 13 means the child has 3 copies of chromosome number 13. Trisomy 18
means the child has 3 copies of chromosome number 18.
When a baby is conceived, a normal egg cell and normal sperm cell start with 46 chromosomes.
The egg and sperm cells then divide in half. The egg and sperm cells then have 23
chromosomes each. When a sperm with 23 chromosomes fertilizes an egg with 23 chromosomes,
the baby will then have a complete set of 46 chromosomes. Half are from the father
and half are from the mother.
But sometimes an error occurs when the 46 chromosomes are being divided in half. An
egg or sperm cell may keep both copies of chromosome number 13 or 18, instead of just
1 copy. If this egg or sperm is fertilized, then the baby will have 3 copies of chromosome
number 13 or 18. If the baby has 3 copies of chromosome number 13, this is called
trisomy 13. If the baby has 3 copies of chromosome number 18, this is called trisomy
18. The extra copy of chromosome number 13 or number 18 is present in every cell in
Sometimes the extra number 13 or
number 18 chromosome, or part of it, is attached to another chromosome in the egg
sperm. This is called a translocation. This is the only form of trisomy 13 or 18
that may be inherited from a parent. Some parents may have balanced translocation.
means the number 13 or 18 chromosome is attached to another chromosome. But it doesn’t
affect their own health.
A rare form is called mosaic trisomy 13 or 18. This is when an error in cell division
happens after the egg is fertilized. People with this syndrome have both normal cells
and some cells with an extra chromosome number 13 or 18.
Symptoms can occur a bit
differently in each child.
A baby with trisomy 13 may have
symptoms such as:
- Low birth weight
- Small head with sloping forehead
- Structural problems of the brain, such
as the front of the brain not divided normally (holoprosencephaly)
- Eyes that are close together
- Nose or nostrils not well
- Cleft lip and cleft palate
- Small jaw
- Low-set ears that have abnormal
- Scalp problems that look like sores
- Purplish-red birthmarks from tiny
blood vessels close to the skin (hemangiomas)
- Extra fingers and toes
- Feet with prominent heels
- Short neck
- Heart defects
- Kidney problems
- Part of the belly (abdominal) organs
bulging through an opening near the umbilical cord (omphalocele)
- In boy babies, testes not descended
into the scrotum
- In girl babies, a uterus that forms in
2 branches (bicornuate uterus)
A baby with trisomy 18 may have
symptoms such as:
- Looking thin and frail
- Failure to thrive
- Problems feeding
- Small size, even when delivered full
- Small head
- Low-set ears
- Small mouth and jaw
- Shortened breastbone (sternum)
- Small pelvis
- Weak cry
- Problems with hearing
- Heart defects
- Can’t extend fingers fully
- Arms and legs in a bent position
- Feet with a curved shape under the
heel, known as rocker bottom
- Spinal cord not fully closed (spina
- Eye problems
- Cleft lip and palate
- Slow growth
- High blood pressure
- Kidney problems
- Curvature of the spine
- In boy babies, testes not descended into the scrotum
Most babies with trisomy 18 have
problems that affect all parts of the body. Heart problems, feeding problems, and
infections are what most often lead to death.
Chromosome problems such as trisomy
13 or 18 can often be diagnosed before birth. This is done by looking at cells in
amniotic fluid or from the placenta (called chorionic villous sampling). This can
be done by looking at the amount of the baby’s DNA in the mother’s blood. This is
noninvasive prenatal screening and can be done on a pregnant woman of any age. These
tests are very accurate.
Fetal ultrasound during pregnancy can also show the possibility of trisomy 13 or 18.
But ultrasound is not 100% accurate. Problems caused by trisomy 13 or 18 may not be
seen with ultrasound.
After birth, your baby may be diagnosed with a physical exam. The healthcare provider
may also take a blood sample. This is checked in a lab to find the extra chromosome.
Treatment will depend on your child’s symptoms, age, and general health. It will also
depend on how severe the condition is. Talk with your child’s healthcare providers
about the risks, benefits, and possible side effects of all treatments.
Severe, often life-threatening health problems occur in both trisomy 13 and trisomy
18. Treatment for complications varies depending on the body organ affected and the
severity of the problem. Your child’s healthcare provider will discuss treatment options
Researchers don’t know how to prevent the chromosome errors that cause these disorders.
There is no reason to believe a parent can do anything to cause or prevent trisomy
13 or 18 in their child.
If you are younger than 35, the risk of having a baby with trisomy 13 or 18 goes up
slightly each year as you get older. After a baby is born with suspected trisomy 13
or 18, a healthcare provider will take a blood sample to do a chromosome analysis
(karyotype). This confirms trisomy 13 or 18. This test also shows the chromosome problem
that caused the disorder. This information is important in assessing the risk in future
pregnancies. Translocation and mosaic trisomy 13 and 18 have different risks for future
Your healthcare provider may refer
you to a genetic counselor. This expert can explain the results of chromosome tests
detail. They can talk about risks for future pregnancies. The counselor can tell you
what tests are available to diagnose chromosome problems before a baby is born.
A diagnosis of trisomy 13 or trisomy 18 can be overwhelming and upsetting. You will
face difficult decisions about how to care for your baby. Many babies born with trisomy
13 or trisomy 18 may not live beyond the first few days or weeks of life. So you may
have to cope with your baby never coming home from the hospital.
Many resources are available to help you. These include early intervention services,
hospice care, social workers, a hospital chaplain or clergy, and genetic counselors.
Support groups that include other families dealing with a similar problem can also
help you cope with questions and emotions.
If you are caring for your child at home, call your child’s healthcare provider if
your child has:
- Symptoms that don’t get better, get worse, or worry you
- New symptoms
- Trisomy 13 and trisomy 18 are genetic disorders. They include a combination of birth
defects, such as severe learning problems and health problems that affect nearly every
organ in the body.
- Most babies born with trisomy 13 or 18 die by the time they are 1 year old. But some
babies with these disorders do survive the first year of life.
- There is no reason to believe a parent can do anything to cause or prevent trisomy
18 or 13 in their child. Researchers don’t know how to prevent the chromosome errors
that cause these disorders.
- A diagnosis of trisomy 13 or 18 can be overwhelming and upsetting. You will face difficult
decisions about how to care for your baby.
- Many resources are available to help you. These include early intervention services,
hospice care, social workers, a hospital chaplain or clergy, genetic counselors, and
Tips to help you get the most from a visit to your child’s healthcare provider:
- Know the reason for the visit and what you want to happen.
- Before your visit, write down questions you want answered.
- At the visit, write down the name of a new diagnosis, and any new medicines, treatments,
or tests. Also write down any new instructions your provider gives you for your child.
- Know why a new medicine or treatment is prescribed and how it will help your child.
Also know what the side effects are.
- Ask if your child’s condition can be treated in other ways.
- Know why a test or procedure is recommended and what the results could mean.
- Know what to expect if your child does not take the medicine or have the test or procedure.
- If your child has a follow-up appointment, write down the date, time, and purpose
for that visit.
- Know how you can contact your child’s provider after office hours. This is important
if your child becomes ill and you have questions or need advice.