"Heavily pregnant." I hate this. There's a frisson of the demeaning about it in my mind with regard to both mother and child. The child is burdensome somehow and the mother sounds tediously weighed down. In any case, "pregnant" is a sort of standalone word that shouldn't take an adverb qualifier. We don't say slightly pregnant or very pregnant; well I don't anyway. There are better ways of indicating the stage in pregnancy that's been reached.

Inconsistently mebbe, I'm fine with qualifying "unique," another allegedly standalone word, not because I've given up the fight but because the meaning of "unique" has drifted. The evolution of meanings of words is time-honoured and is healthy and democratic. A good example is how we now use "decimate." ;-)