That's what foster homes and adoptions are for. And unwanted can easily change to wanted once the child is born. Happens all the time, and throughout all of human history.
Adoptions? We can't even find homes for the kids today awaiting adoption.
Using American Statistics
There are 107,918 foster children eligible for and waiting to be adopted. In 2014, 50,644 foster kids were adopted — a number that has stayed roughly consistent for the past five years. The average age of a waiting child is 7.7 years old and 29% of them will spend at least three years in foster care.Dec 8, 2015
Link
So you propose adding millions of unwanted children to an already overwhelmed system? That's your solution.
You tend to think in a very simplistic way and spout cliches about how in your opinion all this should work.
Here's the deal.
Millions of unwanted children would need to be taken care of and raised. The system we currently have simply could not handle it. We would need to put in place a huge infrastructure network to support and raise millions of unwanted children. This would require very large tax payer funding. It's funny because usually the "right to life" crowd are usually the ones who scream the loudest about welfare moms and welfare bums and eliminating social assistance etc. etc.
The "Right to Life" crowd should more aptly be named, "Right to birth" because once the kid is born, they, like you, just figure that it's "mission accomplished" (yes, that's a George W Bush analogy because we all know how well that worked out) and it's now someone else's problem (like your post when I asked you who is going to raise all of these unwanted children, and your simplistic (even child like) response was, "their parents". I don't know what planet you are on on this one frankly.)
When I pressed you to come up with a realistic solution, your next solution was, "adoption and foster care" and harping on about the good ole days it wasn't a problem (like you would know.)
Well the adoption and foster care system can't handle the kids we do have right now.
So again, I ask you, "what's your plan for dealing with millions of unwanted children"
I await your well thought out response. And waxing poetic with anecdotes about the good ole days is not a solution.
So lets here about how you plan to house, feed, educate, socialize well adjusted children whose parents did not want them.