If funding for fertility treatment was stopped then I believe maternity care should be self funded after a certain number of kids. You want them, you pay for them after all?
Why any kids at all? Pregnancy and birth are not illness and they are a choice, so maybe we should say that the NHS only steps in if there are specific medical complications.
Obviously, we all know that this would be an appallingly terrible and outrageous idea for any number of reasons; but why scrap it after 2, 3, 4 kids? Even if a woman has 20 children, the 20th didn't ask to be born any more than the 1st one did - and has just as much right to a safe, professionally-assisted birth as the 1st.
In fact, much as I think that having very large families tends to be a bad idea for anybody, I still never get the point that some people make about how much each child will cost the taxpayer for their healthcare, schooling etc. as the costs for each individual are front-loaded - 20 children from one family = 20 potential future taxpayers, just as much as 10 x 2 children who happen to be born to 10 different families.
I've still never quite understood why teeth and eyes have to be paid for yourself (except for limited help for children and certain other qualifying groups), but all manner of arguably optional/self-inflicted healthcare needs that happen to affect different body parts are all free. Not that I'm suggesting we should scrap the latter, of course!
I think the basic principles whereby you can qualify for basic, perfectly functional glasses but pay yourself if you want nicer ones, or you can have fillings free but gold ones are self-funded, make good sense; but that is not what we have at all. You hear and meet so many people who are putting off going to the dentist with horrendous tooth pain, because they simply can't afford it, and they end up by default in the exact same category as people who would like more gleaming white Hollywood-style gnashers to look better on Insta, but don't have the funds, regardless of the respective urgency, importance or impact on quality of life of the two scenarios.