The UK has a long established programme of newborn bloodspot screening. This operates under a model of informed choice. Understanding is central to the `informed' element of an informed choice yet it is rarely assessed. To date most research within the context of newborn bloodspot screening has focussed on parental recall of information. In this paper I argue that simplistic assessments of knowledge through recall fail to reflect more complex notions of understanding. In support of this contention I draw on qualitative interviews with parents of children who have undergone newborn bloodspot screening.