Two healthy parents can have a baby with birth defects even if they have no risk factors or health problems. Pregnant women who do everything in their power to have a healthy pregnancy may still have a child with a birth defect. The March of Dimes reports that the cause of nearly 60% of birth defects is unknown. The remaining percent of birth defects is thought to be caused by genetic or environmental factors – or both.

Every person has about 35,000 genes per cell. These genes determine things such as the color of a person’s eyes, their hair color and height and so on. One faulty gene can cause a baby to be born with a birth defect.  A baby inherits his chromosomes -- and the genes they contain -- from his parents. A baby will have one pair of chromosomes from his father and one pair from his mother. A child can be born with a birth defect even if only one half of his chromosomes have a defect or a disease. This is known as dominant inheritance. Birth defects that are sometimes caused by dominant inheritance include dwarfism and Marfan syndrome.   

Recessive inheritance is when the baby has inherited a faulty gene for the same condition or disease from both parents. Recessive inheritance can include conditions such as cystic fibrosis or Tay-Sachs.

Other genetic factors that can lead to birth defects are those which are X-linked. This means a male baby has received a faulty gene from their mothers. The structure or number of chromosomes a baby inherits can also cause birth defects. Down syndrome is a birth defect that is caused by chromosome problems.

There are steps that can be taken to make sure a baby does not have birth defects. However, there is no way to guarantee that a baby will be born without birth defects – even if there is no family history of birth defects.