Hi, If I were your treating Doctor for this case, I would come up with three possibilities, these include: 1.The first possibility is of hereditary, child usually have form of head as parents. Her body is small, that s why it looks as big. 2.The second possibility is of Vitamin D and Calcium insufficiency. It could be beginning of rickets. Vitamin D,Calcium, Phosphorus should be measured to rule out this diagnosis. 3.The last possibility is of Hydrocephalus or high intracranial pressure . For this purpose you need to get an ultrasound -neurosonography. I suggest you to consult a pediatrician, neurologist and get an ultrasound to be confident. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions. Wishing your baby good health.