Neugeborenes, Kleinkind, Säugling. They are still used but in different situation. Kleinkind for example is more used for children between 1 - 4 years old. Neugeborendes is used for children shortly after birth. So I guess you still have Säugling but that doesn't sound so appealing.
my bad, simple typo. But I can't remember why I listed it anyway. It is more like an adjective but I use it sometimes like a noun. People understand me, some others use it too ~ http://www.duden.de/rechtschreibung/Neugeborenes well it is a "substantiviertes Adjektiv" (an adjective that is treated like a noun)