This is an interesting and challenging book that has a proven success record in the Netherlands. To sell 6000 copies in a previous Dutch edition is very impressive and suggests wide acceptance or at least lively debate in that country.
The cross-appeal to both obstetricians and midwives, the relative brevity and low cost are all factors in its favor. I think the likelihood of a successful English edition is good. The American market is tough, though. It can be quite parochial.