Genetic disorders are diseases that can be passed from parents to children. Some disorders may be inherited if only one parent has the abnormal gene, while others can be inherited only if both parents have the abnormal gene.

If one or both parents have a defective gene or have a genetic disorder, the risk of passing the disorder on to a child is the same with each pregnancy. Having one healthy or one affected child doesn't change the odds that future children will or will not be affected.

If the baby's mother or father or anyone in either of their families has a genetic disorder, genetic counseling may help the family decide what type of prenatal testing they want.

Genetic disorders that may be inherited include:

• Cystic fibrosis.
• Sickle cell disease.
• Tay-Sachs disease.
• Thalassemia.
• Hemophilia.
• Duchenne muscular dystrophy.
• Huntington's disease.
• Polycystic kidney disease.

A small number of disorders occur because of a one-time mistake in a single gene (new mutation), such as a change in a gene of one of the parents' egg or sperm cells or because of a change in a gene of the fetus. These one-time genetic changes are unlikely to happen again in future pregnancies.