Why is the crib death rate higher for twins than for singleton babies?
First, if the twins are not the mother’s first pregnancy, often the mother already has a crib mattress. Secondly, many twins sleep in the same crib when they are very young babies, but at some point while still within the crib death risk age are separated so that they are sleeping in separate cribs. Both of these situations require a second mattress to be obtained. As a consequence, it often occurs that one twin in a family sleeps on a previously used mattress, while the other twin sleeps on a new mattress. This has the result that the crib death rate among twins is significantly higher than among singleton babies; also it is statistically much more likely that one twin will die of crib death than the other. The twin sleeping on the re-used mattress is at around double the crib death risk of the twin sleeping on the new mattress.
