Since 2000, polls have consistently shown roughly 50% of Americans identify themselves as "pro life". Those polls also show that a substantial percentage of the pro-choicers favor some restrictions and find the practice personally objectionable.
I'd call that a "significant portion".
"I'd call that a "significant portion"."
Then go ahead and propose a constitutional amendment and be done with it. If you have the support of the vast majority of americans it should be no problem.