IMO the biggest concern is not whether CRISPR-Cas9, and DNA ligase, will do their job reliably (given appropriate guide RNA, and methodology)... the biggest concern to me is that we don't know what else the target SNP tends to do, aside from whatever we've found from GWAS.
Here's an example...
APOE e4 is associated with Alzheimer's disease risk. People in Guatemala have a high prevalence of this allele. Some researchers from the US might decide it's a good idea to fly down to Guatemala and launch a CRISPR clinical trial to 'protect' newborn Guatemalans from this increased risk of Alzheimer's. So they do; come back to the US, have a toast to longevity for these children. It has recently come to light however, that APOE e4 confers protection against Malaria parasites. Not a big deal if you live in Norway - huge deal if you live in Guatemala. Suddenly, the risk of developing an age related dementia doesn't seem all that pertinent.
So, my 2 cents is that, if we're really going to start CRISPRing babies, we'd better be doing our due diligence, and for now limit to diseases that significantly and immediately impair wellbeing.
Here's an example...
APOE e4 is associated with Alzheimer's disease risk. People in Guatemala have a high prevalence of this allele. Some researchers from the US might decide it's a good idea to fly down to Guatemala and launch a CRISPR clinical trial to 'protect' newborn Guatemalans from this increased risk of Alzheimer's. So they do; come back to the US, have a toast to longevity for these children. It has recently come to light however, that APOE e4 confers protection against Malaria parasites. Not a big deal if you live in Norway - huge deal if you live in Guatemala. Suddenly, the risk of developing an age related dementia doesn't seem all that pertinent.
So, my 2 cents is that, if we're really going to start CRISPRing babies, we'd better be doing our due diligence, and for now limit to diseases that significantly and immediately impair wellbeing.