Another element:
I didn't plan on having a kid, I just didn't take consistent enough precaution and had one pregnancy over a ten year relationship.
I don't regret it, but I wouldn't have had children if it was done through careful pre-planning.
I've long wondered about this. How much of this is social inertia of 'next step' in your life and how much is intrinsic desire to do so.
The birth rate isn't dropping because people don't like natural conception. It's dropping because they're choosing not to have babies. When people want a baby, the vast majority have nothing against the typical technique.
Your insistence that these two unrelated issues are somehow linked puzzles me.
If you think any significant number of people adopt children because they just want to avoid pregnancy and birth, you're the one just making things up. I'm sure you can find a few people who do this, but their numbers are utterly insignificant.