Yes, you can file the W-7to get an ITIN for your baby and send with your tax return- you can either use the acceptance agent OR you can send the original documents with the application.
Your baby would have to be at the acceptance agent to get the documents certified- there are international acceptance agents if that is a possibility.
You can either file now without the baby and amend later, or file for an extension- it is your choice (I would file for the extension and use the acceptance agent but this is opinion, either choice is acceptable.
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