One voucher per couple. If you throw it all off on women you're going to create a problem with many men not getting an opportunity to reproduce. You're limiting genetic variance.

You're also going to have to end gender disclosure pre-term. No choosing the sex of your child as that causes problems too.

Vouchers will have to be able to renew if a child dies.

It's never going to be as simple as a voucher for women. That's simplistic and reductive thinking.