Can a Mitzva be done on behalf of an child still in the womb? I.e can I do a donation to a charity in my name, my wife's and my soon to be +1? If so, in what name would that mitzva be done in as +1 doesnt have a name or even a gender yet. My Wife is currently in her 2nd trimester.
Would one be inviting an ayin-hara by doing this?
You cannot do a Mitzva for other people, the same way you cannot breathe, eat or go on diet for other people.
Why? Because a Mitzva generates a spiritual reward that you will enjoy in the world to come.
If you cause other people to do a Mitzva, you get brownie points for that too. Since your children are in existence because of you, you get some credit for their Mitzvot.
What you can do is to pray for other people. The Gemara in Brachot (60a) mentions that you can pray for the health of an unborn baby.
When you give charity, you just became more righteous - in a tiny way - and your prayers are therefore slightly more likely to be answered.
