Reproductive rights are human rights
I'm originally from Brazil, a third-world country where abortion is illegal. This fact doesn't prevent abortions from happening at all. Everyone knows someone who did it. I'd even go as far as saying someone in every single extended family in Brazil has certainly done it, whether you know it or not.
The difference is all these procedures were clandestine and many were unsafe, unsanitary, dangerous and unnecessarily painful.
The only outcome of making abortion illegal is endangering people's lives. Full stop. You're not preventing it from happening, you're only preventing it from happening safely.
The decision to have an abortion is never made lightly, at least not by people who will actually go through the procedure. Having a child is a life-changing event with huge responsibilities that literally last a lifetime. Due to obvious reasons, people with uteruses can get caught in situations where this decision and all its repercussions is up to them.
On the other hand, men who want to prevent an “accident” from becoming an inconvenience – powerful men, conservative men – won't think twice about suggesting or imposing it, no matter if it's legal or not.
If you're lucky they'll pay for it. If not, well...
Land of the free, unless you're talking about healthcare
The United States, a rich conservative country with no state-sponsored healthcare, is about to make abortion illegal. The supposedly progressive government is not really interested in doing anything to prevent it. The lack of public healthcare means all illegal abortions that will still happen – like it or not – will be much more unsafe, unsanitary, dangerous and unnecessarily painful.
It will happen to people you know in your extended family. Maybe powerful men, conservative men, will offer to pay for it if an “accident” inconveniences them – as they always have.
But now it will also be clandestine, and they won't be the ones going to jail.
Raising children costs money – a lot of money. Children are fragile and tend to fall on their faces all the time. I heard they also get sick quite a bit. Hell, giving birth costs upwards of USD 30k if you do it on the cheap.
At least Brazil has universal healthcare.
“But my religion!”
I won't get into religious arguments here. They don't matter. Many people who follow your religion had abortions, and it's very likely that includes someone you know.
Picketing Planned Parenthood, restricting access to contraceptives, being against sex education and setting up fake abortion clinics don't make anything better either. How contradictory is being against abortion and education/resources to prevent pregnancies at the same time?
Religious people are totally ok with forcing people to give birth. They're not pro-life, they're pro-forced birth.
Fake moral superiority
Many people think they're “better” for being pro-forced birth. They'll call anyone defending reproductive rights “baby killers”. Of course they don't care about children as much once they make their way out of the uterus, so don't you dare ask about government-sponsored childcare or anything remotely resembling a safety net.
Of course I'm not the first person to say this. George Carlin did it much better back in 1996 and anything I say – maybe a bit more politely – won't explain it any better. So I'll leave it at that.