The only traditional song I know that specifically mentions abortion is Tamlin. The lyrics in the version I sing refer to abortion when she finds herself pregnant--

Then up and spoke another serving girl; "Ever and alas!" said she; "I think I know a herb in the merry green wood, That'll twine your babe from thee, Lady."

So Margaret's taken up her silver comb; Made haste to comb her hair; And she's away to the merry green wood As fast as she can tear, can tear...

But she hadn't pulled a herb in that merry green wood-- A herb but barely one-- When by her stood young Tamlin Saying, "Margaret, leave it alone, my love..."

"Oh why do you pull that bitter little herb, That herb that grows so grey, To take away that sweet babe's life, That we got in our play, my dear?"

etc.