How does the hospital tell if a baby has been subject to the mother doing drugs if no one talks about it?

The baby doesn't act naturally if it has drug in it or if they have been subdued to it for a long time so they have fetal damage. The people at the hospital are experts on this and if you care about the baby you will tell them so the baby can get help in the future when they get problems. If they suspect anything they will test the baby.