Translation guide
In Japanese, expressing 'newborn' depends on whether you're referring to a baby, an animal, or using it as an adjective. The most common term for a human newborn is 新生児, but in everyday conversation, 生まれたばかりの赤ちゃん is more natural. For animals, use 生まれたばかりの～.
Referring to a baby that has just been born, in medical, formal, or everyday contexts.
Describing an animal that has just been born.
Attach the animal name after の. This is the standard way to say 'newborn [animal]'.
Using 'newborn' as an adjective for things like 'newborn star' or 'newborn nation'.
Works for metaphorical newborns as well, like a new nation or idea.
a newborn nation
新生児 is strictly for human newborns. Using it for animals sounds odd. Use 生まれたばかりの～ instead.
In Japanese, you can often just say 生まれたばかり (just born) without 赤ちゃん if the context is clear. For example, 生まれたばかりで、まだ目が見えない (Since it's just born, it can't see yet).
The standard medical and formal term for a human newborn (up to about 4 weeks old). Used in hospitals, official documents, and news.
Newborns drink milk many times a day.
The most natural, everyday way to say 'newborn baby'. Literally 'a baby just born'. Suitable for casual conversation.
My friend has a newborn baby.
General word for 'baby'. In context, it can mean a newborn, but it's not specific. Use when the newborn stage is clear from context.
We had a baby! (literally: A baby was born!)
Same as above, but used in compound terms like 新生児室 (newborn nursery).
There are many babies in the newborn nursery.
Newborn kittens can't see.
The newborn puppy is drinking milk.
Means 'new' and can be used in formal or literary contexts for something newly created.
A newborn hope was born.