@ibilly That is incorrect -
Carpenter did show increase in absence of alcohol use, drug use and preterm birth.
It found that
for babies less than 3 months old, who are exclusively breastfed, have nonsmoking parents, and whose mothers had not had any alcohol or drugs in 24 hours, the increased risk of SIDS because of bedsharing was 5x (I know OP's baby is four months old - I just want to correct your point above).
Carpenter also found that smoking, alcohol and drug use significantly increase the risk beyond that to up to 18x more risky.
Bedsharing has increased in the US, and SIDS has fallen, that's true. However, most parents use SIDS as the catchall term for "babies died in their sleep." Not to get too in the weeds, but the term for 'babies died in their sleep' is Sudden Unexpected Infant Death. That term encompasses refers to 3 death codes (R95 [SIDS], R96 [unexplained sudden death in children] and W75 [accidental suffocation or strangulation in bed]).
SIDS rates did
fall between the 90s and 2015, but deaths coded as W75 (suffocation) rose by 184%.