Infants in crib.

Natalie
My friend had a baby six weeks ago that has been sleeping fine in crib but now that she's getting bigger she bumped her head and had her arm caught between slates. (Separate occasions) My friend doesn't want to use bumper guards because of SIDS risk. 
Anyone else have a similar problem? I was planning on using crib too, so just curious of other people's experiences and if this is common with infants in cribs.