Bioethnography, the combination of ethnographic observation and biochemical sampling, is a synthetic method for understanding environmental and bodily interactions. DOHaD researchers can use bioethnographically derived data to examine the complex processes that shape health and disease. Using examples from a longitudinal birth cohort study in Mexico City, the authors describe how bioethnography, which begins with an open-ended observational stage, can counteract some of the limitations of DOHaD research, which can be reductionist and universalising. DOHaD researchers often focus on the behaviour of individuals, especially mothers, instead of on the political-economic processes and environments that contribute to poor health and inequality. In addition, DOHaD researchers, who often reside in high-resource environments, tend to universalise their own experience rather than identify relevant research questions for people living in different circumstances. To combat reductionist and universalising tendencies, bioethnography allows researchers to develop inductively derived hypotheses and then test these in specific contexts. Validating and testing theories derived from bioethnographic methods in the same population where they were observed can fill critical gaps in DOHaD research that seeks to understand the complex relationship between environments and disease over the lifecourse.