Birth injury refers to damage or injury to the child before, during, or just after the birthing process. "Birth trauma" refers specifically to mechanical damage sustained during delivery (such as nerve damage and broken bones).

The term "birth injury" may be used in two different ways:

Birth injuries must be distinguished from birth defects. "Birth defect" refers to damage that occurs while the fetus is in the womb, which may be caused by genetic mutations, infections, or exposure to toxins. There are more than 4,000 types of birth defects.

Difficult labor, also known as dystocia or obstructed labor, occurs when the child cannot easily pass through the birth canal. This can result in fetal distress or physical trauma to the child, especially broken clavicles and damage to the brachial plexus nerves. It can also deprive the child of oxygen as the umbilical cord is pinched, potentially causing brain damage or death.

Difficult labor may occur because the baby is abnormally large (macrosomia), because the mother's pelvis or birth canal is small or deformed, or because the baby is in an abnormal presentation for the birth (such as breech or transverse presentation).

Fetal malformations and birth injuries may occur as a result of exposure to environmental toxins such as mercury or lead. Many medications can also affect the development of the fetus, as can alcohol, tobacco, and illicit drugs. Birth injuries may also occur during delivery and labor, in some cases as a result of medical malpractice.

Genetic mutations can cause a wide variety of fetal malformations, ranging from relatively mild cleft lips to severe and even fatal deformities.

Maternal infection may be transmitted to the fetus; this is called a vertically transmitted infection. The fetus has a weak immune system, so infections that are relatively minor in adults can be serious in a developing fetus. In addition, some studies suggest that maternal infections increase the risk of neurodevelopmental disorders, including schizophrenia, in the child.