Invited commentary: is prenatal fasting during Ramadan related to adult health outcomes? A novel and important question for epidemiology.

In this issue of the Journal, Van Ewijk et al. (Am J Epidemiol. 2013;177(8):729-736) report intriguing associations between prenatal exposure to the religious month of Ramadan and body anthropometry among adult Muslims in Indonesia. They categorized prenatal exposure according to the relative timing of Ramadan and the individual's birth date. Because the data were derived from a study of adults, they could not determine whether an individual's mother had fasted during Ramadan or not. Therefore, they used an intention-to-treat analysis to compare the outcomes for groups categorized as unexposed with the outcomes for groups categorized as exposed during specified periods of gestation. Periconceptional exposure to Ramadan was associated with a 0.8-cm reduction in average adult height. Exposure in mid- or late gestation was associated with slightly lower adult weight. We address 5 questions raised by this study: 1) Can Ramadan fasting be considered a mild form of acute starvation?; 2) Are the findings consistent with other knowledge about prenatal nutrition and offspring outcomes?; 3) Are there other explanations for the associations that were found?; 4) Are the results internally coherent and robust enough to support the 2 main findings?; and 5) What strategies could be used to further advance this important field of research?