Sids happens when a baby is in a crib, alone.
Sids death kills about 5000 babies a year in the usa.
Only between 49 and 64 infants a year die from cosleeping.
Most of those are parental error, such as the parent(s) being drunk or high on drugs or other medication and rolling over and smothering. Or a parent trying to cosleep on an unsafe surface (such as a waterbed).
Cosleeping is actually safer then crib sleeping if you do it properly. It has been shown to help regulate your newborn's breathing and limit the amount of apnea spells. The mother's body also naturally does not go in to the same deep sleep as it would when she's alone so the risk of rolling over is quite slim unless you are on medication or a very heavy sleeper in which case no, you shouldn't cosleep.