The time around conception and the first trimester are crucially sensitive periods, and the consequences of patterns of drinking that can expose the fetus to high ethanol blood concentrations are of particular concern (9). The uncertainty on longer-term effects of in utero exposure to ethanol into childhood and even adulthood arises from unreliable reporting of alcohol intake leading to measurement error, as well as residual confounding typical of standard observational studies. For example, it has been suggested that up to 1% of all children could suffer impaired neurodevelopment as a consequence of prenatal alcohol exposure, but solid evidence is lacking (2). This highlights the importance of using alternative study designs that control for some or all of these problems, and finally allow interpreting association as causation.
