Clumsy baby, should I be concerned?

Child development is an uncertain science, although there are various statistical studies done on which child development charts are based, it is still not a perfect science. As you stated, children may or may not fit within the developmental guidelines established by the American Pediatric Society, but this does not mean that there is a physical or mental issue to the child's well being. Like you said some children are simply clumsy. on the other hand, things like deafness, poor vision, or even orthopedic problems can cause unsure footing, falling and other accidents. The best course of action if you are concerned would be a visit to your pediatrician where you can voice your concerns and tests can be run to rule out illness or vision and hearing problems.

I wouldn't be very worried about the clumsiness. My now 6 year old daughter was the most clumsy child I had ever seen...she was always falling and getting hurt and such. She is still a  tad clumsy but as she grew older gained more control over her actions the clumsiness gradually went away.