Please let me know how old the baby is ? is he an infant ?
The common cause for reddish spots over the spine in the midline are what is called 'hemangioma'. These usually get better by themselves as the child grows. However, you must show it to your pediatrician
as a midline swelling will need atleast an Xray of the backbone to make sure all is well on the inside. Without alarming you, i would encourage you to atleast post a picture of the red spots on this forum or email them or visit your doctor.
Please do not hesitate to contact me if you have any clarifications
Dr Antony Robert C