The exposome--exciting opportunities for discoveries in reproductive and perinatal epidemiology

Understanding the mechanisms that underlie successful human reproduction and development is an ambitious goal, given the many unique methodological challenges surrounding such study. These challenges are well understood by reproductive and perinatal epidemiologists and include its conditional nature, unobservable yet informative outcomes such as conception, multi-scale missing data, correlated or non-independent outcomes, interval censoring and a hierarchical data structure. Novel methodologies for overcoming these challenges and for answering critical data gaps are needed if we are to better understand the inefficiency that currently characterises human reproduction with the goal of improving population health. The exposome is an emerging paradigm that offers promise for understanding the natural history of human reproduction and development, and its many associated impairments that develop later in child- or adulthood. This novel paradigm recognises the need to identify and measure the totality of environmental (non-genetic) exposures from preconception through sensitive windows, and to identify patterns associated with healthy and adverse outcomes. The exposome accommodates research focusing on unique subpopulations, such as couples undergoing assisted reproductive technologies, so that methodological limitations such as unobservable and conditional outcomes can be better addressed. Reproductive and perinatal epidemiology is uniquely suited for proof-of-concept exposome research, given the intricate relations between fecundity, gravid health and later onset disease and the narrow and interrelated sensitive windows that characterise the conditional nature of human reproduction and development. Bold new conceptual frameworks such as the exposome are needed for designing research that may lead to discovery and improve population health.