When I was an atheist before reverting to the Catholicism of my youth, I was pro-life.
Perhaps having been adopted (in 1958) has something to do with it.
However, also as a scientist, I found any cut-off point for where life “begins” to be highly arbitrary. The fact remains that the genetic signature of a unique human individual begins a few moments after the ovum is fertilized. Any other point beyond that, is arbitrary. Therefore from that point forward, life deserves protection.
So yes, an atheist can be pro-life, moral, ethical, etc.
The real question that much more interesting is where did the atheist get those ethics from?
I would argue, even if the atheist doesn’t believe them, in very large part from Judeo-Christian religious ethics (at least in our cultures). At least the foundations.