Nice comments Emilia. Epigenetic modifications do show specific timing in humans (though not quite the same as in mice) - so if epigenetics are the major mediators there are probably at least "sensitive" developmental periods when adverse exposures are differentially influential, even if those might be partially offset by later events. The big distinction between Weaver and Gruenewald is the emphasis on a critical period in early life versus the accumulation of disadvantage. The latter hypothesis gives much more optimism that we can intervene in adulthood to substantially ameliorate disparities.
Maria