I don't know whether this is a completely personal thing, or comes from my Chinese cultural background, but I do not think it makes sense to have newborn babies instantly granted the moral standing of a full human. For entities with low self concept, like animals, human babies, or severely mentally handicapped humans, I think their moral standing should be based on the attachments that other people have (or potentially have) to them. Also, somewhat based on the fact that the more something seems human (even if they are not fully functionally human), the more the way society treat them will tend to color how all humans are treated.

So, in my opinion, there is a continuum even after birth. For example, I think it is wrong to be verbally cruel to a person who understands what you are saying because you are doing psychological harm to them. But if you said the same thing to a brain-dead person, it's not doing any harm to them. It would be wrong for a parent to physically restrain their 20 year old, normally functioning son and force him to get circumcised, because it would psychologically harm him to have his own determination of his body violated. It is not wrong for a parent to force their infant son to get circumcised, because the amount of harm to them is low. Similar with ear piercing for infant girls, versus forcing a normally functioning 20 year old to do it.