Well the only way to prove it is, as I said before, to let the zygote have time to decide.
I suggest leaving things as they are for 20 years.
At that time, ask zygotes if they believe they would still be here had their mothers chose abortion.
Tally the yes and no votes. (I suggest a sample size of several thousand from a generous racial cross section.)
I predict an overwhelming majority against abortion.
This is a falsifiable proposition and I challenge any scientifically minded group or individual to sponsor the study.
A corresponding study could be undertaken by saving the residue from several thousand contraceptive devices. (You have room in your garage, no?)
After 20 years ask the residues the same question and total the answers, yes or no. I'm sure you can find the words.
I predict insufficient data for verification or falsification.