The bones in a newborn baby's head aren't tough and fixed like an adult's. Instead, they're soft and able to move around to allow the head to pass through the mother's vagina. Because of this softness, certain lumps and bumps may occur on the head. Most disappear after several days. Moveable lumps usually aren't serious. However, in rare cases, the lump may signify a more serious condition known as hemorrhagic condition of the newborn.
A small moveable lump on a newborn or very young baby's head is often caused by cephalohematoma, according to Mary M. Gottesman, Ph.D., R.N., C.P.N.P., F.A.A.N on the Netwellness website. This is a little pocket of blood, often caused during labor contractions and the stresses of delivery. In most cases, the blood causes no real health risk. It simply hardens over time to create the lump, then slowly dissolves as the baby grows -- often taking over six months to disappear completely.
Your baby's head has gaps between the soft skull bone plates. The spaces also allow the head to expand as the brain and body grow. However, these gaps may allow pockets of fluid to collect at the scalp. Often, these move a little to each side when you touch them. The fluid bubbles are called caput succedaneum, according to the University of Maryland Medical Center. In most cases, these disappear within a few days or weeks.
Hemorrhagic disease of a newborn baby is a rare condition that affects babies with very low vitamin K. Most babies born in U.S. hospitals receive vitamin K shots at birth or shortly afterward to prevent this disease. One possible symptom is a small lump under the scalp caused by bleeding. If you notice a lump and you baby didn't have a vitamin K shot, or if your baby has conditions such as diarrhea, hepatitis, celiac disease or cystic fibrosis, consult your doctor right away.
Lumps in the head that don't move when prodded often suggest more serious problems than moveable lumps. However, if you notice your baby display any additional symptoms, such as lethargy, nausea or diarrhea, always take her to a doctor immediately. If your baby's only symptom is a lump on the head then get the lump checked by a doctor, though it's unlikely to be a serious problem.