Numerical limits in donor conception regimes: genetic links and 'extended family' in the era of identity disclosure.

This article critically examines the setting of limits on the number of children or family groups that may be formed with a single donor in assisted conception regimes. Originally, under conditions of anonymity, numerical limits were said to contain the risk of inadvertent consanguinity between offspring who would not know, and could not know, that they were genetic half siblings, and also between donor and offspring. The increasing embrace of identity disclosure regimes has led to calls for stricter numerical limits based on the purported harm of being exposed to 'too many' genetic relatives in the future. This article asks: how many is too many? And how do we know? The UK and Australian positions are examined, and placed alongside a discussion of qualitative research involving interviews with twenty parents of donor conceived children.