When choosing a crib, avoid antiques or heirlooms. Older cribs may be weak with age or covered with lead-based paint. You want a new or very recently handed-down crib with a label stating that it meets the Consumer Product Safety Commission's standards. The bars on the bed should not be more than 2 3/8 inches apart; be sure there are no splinters or cracks in the wood. The mattress should adjust up and down, and at its highest should still be 26 inches away from the top of the railing. The corners of the crib should not have posts or knobs sticking up above the rail; this is important because you don't want baby to get stuck and hurt in the actual crib structure.
You'll also want to buy a firm mattress that fits tightly into the crib. You shouldn't be able to get more than two fingers between the mattress and the crib's side. Rim the crib with bumpers that stay upright, are tied to the crib, and don't flop over. They should go around the entire perimeter and snap or tie on securely.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.