There needs to be a big cultural shift. People really have to start taking responsibility and start planning in case of job loss, relationship breakdown, abandonment, and death. Circumstances change - sometimes rapidly - and all outcomes need to be carefully considered before bringing more children into the world. Contraception is free. Emergency contraception (the terribly named 'morning after pill') is free from some locations. Yes, we all know that contraceptives fail, but surely the most of us are aware that having sex in the middle of your cycle presents a risk.
It's slightly more complicated for those who try for a baby and end up with multiples. I don't know what to suggest about that.
CMS needs to become mandatory. I don't have experience with it, but too often I see "DC's Dad won't pay CMS" threads. It should be linked to the baby's birth certificate. If the father buggers off, he automatically has to pay X amount. If the mother buggers off, she has to pay X amount. If both abandon their children, they need to pay X amount to whoever ends up looking after the poor child.
As for this comment: Wow there’s a lot of hate for people with larger families on this thread, I don't think that's necessarily the case. But there is a lot of frustration for those who never could have afforded to have a big family, but choose to do so because of hands outs and the ease of not having to work. "I'm going to have another child so I don't have to work" was something one of them said to me. We need a cultural shift.