Sure, I think we can factor in a pregnancy, but...

1. Mak' up yer goon, my bonnie lass,
And mak' it neat and fine,
And ye shall be the plooman's wife,
For the gairdner's changed his mind.

2. The plooman lad, he's hearin' this,
Just in a bush near by;
Says, "Say nae mair, my bonnie lassie
For ye ken better why. "

If the plowman is nearby and hears verse 1, then who's singing it?
========
The plooman lad, he's hearin' this,
Just in a bush near by;
Says, "Say nae mair, my bonnie lassie
For ye ken better why. "

What's that supposed to mean? If it's supposed to be a proposal, it's more frightening than comforting. Then the story stops at that ambiguous moment.