An unborn baby should naturally have a certain amount of fluid surrounding its brain, this is called cerebrospinal fluid or CSF. This fluid surrounds the brain and the spinal cord and flows through the brain's ventricles.
Cerebrospinal fluid has many functions including cushioning the brain, alleviating pressure and balancing the chemicals within.
Too much fluid on the baby's brain is called hydrocephalus, which means "water on the brain." When the ventricles in the brain receive too much fluid, it creates swelling, putting pressure on the brain and possibly damaging it.
Hydrocephalus can be diagnosed by ultrasound. If unable to diagnose with ultrasound, the diagnosis may be confirmed after birth by testing through an MRI or CAT scan.
Hydrocephalus may be caused by a blockage in the brain that prevents the natural flow of the fluid, problems with the baby's body absorbing the fluid or the body's overproduction of CSF.
Hydrocephalus is often treated with surgery to put in a shunt to help drain excess fluid. Drugs may also help reduce the amount of fluid being produced. Surgery has also been conducted while the baby is still in the womb.