“My baby's head size is big. Is it due to any abnormality?”

The doctors will follow the evolution of the curve of the head circumference and corrolate with his growth and his behavior as well as with imaging with ultrasound, ct or mri

The baby may be autocorrecting for the large head diameter as normal growth curves are achieved, if not then a medical evaluation is warranted with head ultrasound or scanning.

That typically would be evaluated by your pediatrician. It is possible for water on the brain or other abnormalities inside the head to cause the head size to be abnormally large. It is also possible that the child just has a large head but on the inside things appear normal.

Could just be a physical difference. The size of the parent's heads should also be considered.

He should be seen by a paediatric neurosurgeon.

Find the soft spot on the top of the babies head. IF it feels full, the problem could be Hydrocephalus (water on the brain). If not he is probably ok, but I would check that. Also during his healthy baby checkup, what percentage was his head circumference and his overall percentages of weight and height? If it is significantly greater than the weight and height percentages, it may be of concern. To relieve your concerns it might behoove you to see a neurosurgeon to be sure.

It is difficult to give a complete answer to the question, because I don't have details about the head measurement and so on. Often babies have large heads and this is not of any clinical significance--often large heads, for example run in families.
Sometimes, however, abnormally large heads can be indicative of serious problems such has hydrocephalus or other problems inside the skull. Since most pregnancies nowadays include fetal ultrasounds, I'm assuming that the doctors knew that the ultrasounds did not show any problems such as hydrocephalus inside the skull.

Signs that would be worrisome are: 1. If the head growth after birth is abnormally rapid (pediatricians routinely measure head size on well baby visits and chart them comparing to normal sizes. 2. If the fontanelle (soft spot on the top of the babies head) is bulging or tense. 3. If there are other neurologic signs such as excessive irritability, delayed development of normal milestones, seizures, crossed eyes.

Bottom line: It is likely that the head size is not of serious consequences, but a full discussion with your pediatrician is appropriate because of the concerns that sometimes a large head size (especially if the head growth is abnormally rapid) can indicate a serious problem which needs prompt attention.

Your baby's head should also be getting larger with time as he grows. If the head size is getting too large too fast then this may be a sign of a problem (such as hydrocephalus, or water on the brain). Your pediatrician needs to evaluate your baby's head size and compare it to a head circumference growth chart. If it is consistently above the 95th percentile, he should be evaluated by a pediatric neurosurgeon.