Hydrocephalus is a developmental problem that causes the head to enlarge. It occurs in about 1 in 1,000 babies and is responsible for about 12% of all severe fetal malformations found at birth.
Hydrocephalus occurs with the development of the brain and central nervous system of the baby in early pregnancy. Spinal fluid circulates around the brain and spinal cord, and must be able to flow without restriction. If openings are blocked and the flow of fluid is restricted, it can cause hydrocephalus (sometimes called water on the brain). Fluid accumulates and causes the baby's head to enlarge.
Hydrocephalus is a symptom and can have several causes, including spina bifida, meningomyelocele and omphalocele. Sometimes intrauterine therapy—treatment in some instances while the fetus is still in the uterus—can be performed.
There are two ways of treating hydrocephalus inside the uterus. In one method, a needle is passed through the mother's abdomen into the affected area of the baby's brain to remove fluid. In the other method, a small plastic tube is placed into the area of fluid in the fetal brain. This tube is left in place to drain fluid continuously from the baby's brain.