"Dwarfism" generally describes a group of
skeletalSkeletal limb abnormalities growth problems (
skeletalSkeletal limb abnormalities dysplasia) that usually result in abnormal length/growth of the bones, and is particularly noticeable in the long bones. These are genetic syndromes and are not acquired. In the vast majority of skeletal dysplasias, the disorder is apparent at the time of birth due to abnormal measurement ratios of the bones.
In terms of growth hormone, prematurity and intraventricular hemorrhage are not generally associated with growth hormone deficiency unless there are problems with other hormones also. It is most likely that your granddaughter's small size is due to her former general illness and prematurity. Babies like her need a tremendous amount of nutrition to achieve "catch up" growth, which can sometimes be hard to obtain if she doesn't eat extremely well.