is caused by the mother sneaking into the baby’s room and killing them?

Yes! It's such a common and well known phenomenon that in many countries a mother killing her baby is not considered a murder. It's considered infanticide, which is a lesser crime:

In New Zealand [...] Where a woman causes the death of any child of hers under the age of 10 years in a manner that amounts to culpable homicide [...] she is guilty of infanticide, and not of murder or manslaughter, and is liable to imprisonment for a term not exceeding 3 years

In Canada [...] The maximum sentence for infanticide is five years' imprisonment; by contrast, the maximum sentence for manslaughter is life, and the mandatory sentence for murder is life.

Are you fucking kidding me? We are in such a cucked society that we allow women to murder their babies with little to no repercussions.