Germ Line changes - arguments
Those who argue in favour of germline changes want to get rid of genes that cause inherited disease e.g. cystic fibrosis. Amber Carrol1 argues that such a move would remove the need for somatic therapy. But that argument doesn't hold, as some genetic variations occur in each generation. Somatic therapy might still have a place, both therapeutic and within a beauty treatment market, where the additional or removal of characteristics might become possible through such therapy.
Arguments against germline changes say that there are already paths to prevent passing disabling genes to offspring. (again from Amber Carroll1)
For many parents 1, 2 & 3 would not be having their own child when 4 and 5 are possible. Also prenatal screening might lead to more undesirable emotional burdens than preimplantatin diagnosis. If this is the path, i.e. if germ line changes remain undesirable and illegal, then couples in this circumstance desiring to have children with a particular genetic contribution would perhaps be best to go for the IVF treatment.
This raises important questions. IVF was not designed for selection in this manner. It was set up to enable childless coupled to have their own children when other methods had proved impossible. This would raise the spectre of IVF becoming a point of eugenic control and this needs full exploration on its own.
1. Human Values in a genetic age. Amber Carroll, 2000, isbn 0 85319 064 X