Congenital differences refer to health conditions or physical traits a baby is born with. These differences can impact how a part of the body looks, works or grows. Some may be visible at birth, while others may show up later in life.

They can impact the heart, limbs, brain, spine or the way organs form or arrange themselves in the body. Congenital differences can occur for many reasons. These include gene changes, exposures during pregnancy or a mix of both.

Some congenital differences are mild and need little or no treatment. Others may need surgery or long-term care.

Congenital differences can happen because of many different reasons. Below are some common causes.

Genetic Diseases

Genetic diseases can lead to congenital differences. These differences come from changes in a person’s DNA. These changes can impact how the body grows, develops or works.

Many genetic diseases can lead to congenital differences. Two examples include Down syndrome and cystic fibrosis.

Teratogens

Early in pregnancy, anything in the mother’s blood can reach the baby. This happens once the fertilized egg attaches to the uterus. Teratogens are substances that can harm the baby during pregnancy.

Teratogens that can cause congenital differences in babies include:

• Alcohol: A baby can have fetal alcohol syndrome if their mother drinks alcohol during pregnancy. That can cause the baby to have a smaller head and brain. They can also have differences in facial features, organ function or organ growth.
• Phenytoin (Dilantin): Taking this seizure medicine in early pregnancy can raise the risk of growth delays or heart problems. It may also cause differences in facial features, fingers or nails.
• Chickenpox (Varicella): If a woman gets chickenpox in the first 20 weeks of pregnancy, there’s a small risk of congenital differences. These can affect the skin, bones or brain. Infection near delivery can be very harmful for newborns, but doctors can give medicine to help protect the baby.

Unknown Causes

Congenital differences can sometimes happen for unknown reasons. While many cases come from genetics, infections or exposures during pregnancy, doctors can’t always find a clear answer. Doctors call these idiopathic, or unknown cause, congenital differences.