Miscarriages and natural failures to implant are not deliberate killings. Christians believe that God has the power of life and death; we don't.
So it is OK for nature to kill, and you should do nothing about it?
If God decides to make a woman miscarry at one day, should we do nothing?
What about one week?
What about one month?
What about 28 weeks?
When do we intervene? Or do we intervene? Who decides?
What if a woman miscarries at 15 weeks? Should we do what we can to save it?