Most brain malformations begin long before a baby is born. Something damages the developing nervous system or causes it to develop abnormally. Sometimes it's a genetic problem. In other cases, exposure to certain medicines, infections or radiation during pregnancy interferes with brain development. Types of brain malformations include missing parts of the brain, abnormal growth of certain parts of the brain, and incomplete division of the brain.
There are head malformations that do not involve the brain. Craniofacial disorders are the result of abnormal growth of soft tissue and bones in the face and head. It's common for new babies to have slightly lopsided heads, but parents should watch the shape of their baby's head for possible problems.