Trisomy 18 is a genetic condition that is the result of an extra chromosome 18. Typically, people have two copies of chromosome 18 in every cell in their body. People with trisomy 18 have three copies of chromosome 18 in every cell. Having too much genetic material (chromosomes) leads to health and learning difficulties. Since the extra chromosome is found in every cell in the body, it can not be removed.
Babies with trisomy 18 have very serious mental and physical disabilities. Many pregnancies with trisomy 18 will miscarry.
Most babies born with trisomy 18 do not survive past the first few months of life.
In general about one in 6,000 births has trisomy 18. The chance of having a child with trisomy 18 increases with the pregnant person’s age.