Miscarriage, economic downturns and causality

There is a really interesting piece and ensuing discussion in recent American Journal of Epidemiology:

“Spontaneous Pregnancy Loss in Denmark Following Economic Downturns” http://aje.oxfordjournals.org/content/183/8/701.full?etoc

I find this interesting for a lot of reasons, including that it suggests another respect in which health and economic well-being are linked. But I am particularly curious how potential outcomes enthusiasts would respond to this sort of study, given that an economic downturn is neither a well-defined intervention nor susceptible to one.