Why do some pro-abortion people avoid using the word abortion and instead use euphemisms like "reproductive rights"?

It's more than just abortion. Some abortion opponents (for instance, the Vatican) also oppose contraception.

Reproductive rights are comprised of more than abortion, it includes birth control, privacy, and the basic right of a person to decide what happens to their body. It even includes things like pregnancy, and alternate methods of getting pregnant, surrogacy and IVF.
Abortions are more properly termed terminations. But either can be used. A spontaneous abortion is the proper medical term for a miscarriage. I've seen anti-choice groups include those as if they were decisions.
We're also not pro-abortion, we're pro-choice. There isn't anything wrong about having a larger vocabulary. It won't hurt you.

Usually when people use the term reproductive rights, they're talking about more than just abortion.
They're talking about a wide range of rights revolving around contraception, sex education, pregnancy, and even parenting.
I've yet to see anyone use reproductive rights as an euphemism for abortion.

I don't care what terminology you use.

You can keep calling it "baby killing" for all I care.

You're the one who looks stupid when you do it..... don't let me stand in your way.... you're doing GREAT at looking like a total moron.

Because no one is pro-abortion.

Cuz it makes them sound better

Because 'not taking responsibility for my sexual behavior at the cost of a baby's life' takes up too much space?