In terms of limitations, our ascertainment of the timing of the exposure meant that it was not possible to specify any particular risk period during the pregnancy. We did not have information on first trimester binge-pattern drinking. The differences in our findings compared to other studies may also reflect other methodological factors such as sample size, ascertainment of drinking behaviour by self-report questionnaire rather than interview (the latter might lead to under-reporting), number of binge episodes and levels of background drinking. In particular, our definition of binge-pattern drinking may have under-estimated risk when compared with studies using binge drinking definitions that reflect alcohol consumption over a shorter duration or studies assessing the impact of frequent binge episodes [37]. However, our findings highlight potential risk to the offspring through exposure to a minimum of 32 g of alcohol. Finally, other study limitations include the possibility of unmeasured or residual confounding (for example, we did not have information on family history of ADHD), the mental health outcome measures were based on a brief questionnaire (SDQ), sample attrition involving missing data on the
