Zika observed in the process of destroying developing brain cells:

http://www.bbc.co.uk/news/health-35725744


Joe sez: Catholic teaching is very clear that life begins at conception
Greg_F sez: Only very recently - historically, that was not Catholic teaching at all.
I suppose that may be true, Greg, but I'd like to see your documentation.

Aquinas thought the soul entered the foetus at 40 days gestation for boys and 80 days for girls. He got the idea from Aristotle. It's somewhere in the Summa Theologiæ but not in the volumes I have.

That period is not relevant to the present issue, but it does show that Catholic doctrine on abortion can change.