Infants born more than 10 weeks early are at highest risk for this type of bleeding. The smaller and more premature an infant is, the higher the risk for IVH. This is because blood vessels in the brain of premature infants are not yet fully developed. They are very fragile as a result. The blood vessels grow stronger in the last 10 weeks of pregnancy.
IVH is more common in premature babies with:
- Respiratory distress syndrome
- Unstable blood pressure
- Other medical conditions at birth
The problem may also occur in healthy babies who were born early. Rarely, IVH may develop in full-term babies.
IVH is rarely present at birth. It occurs most often in the first several days of life. The condition is rare after 1 month of age, even if the baby was born early.
There are four types of IVH. These are called "grades" and are based on the degree of bleeding.
- Grades 1 and 2 involve a smaller amount of bleeding. Most of the time, there are no long term problems as a result of the bleeding.
- Grades 3 and 4 involve more severe bleeding. The blood presses on or leaks into brain tissue. Blood clots can form and block the flow of cerebrospinal fluid. This can lead to increased fluid in the brain (hydrocephalus).