Juxtaposition, contract and irony.
To justapose colors and vibrancy with such a dark concept/issue of killing a fetus would be quite interesting. It almost makes light of what is happening and reflects how light the issues seems to be taken or carried out. Like a joke of some sort.
Further, the audience may have to double take when looking at the piece. As at first they perhaps see something beautiful and then are confronted with the inhumane act.