Recent advances in data acquisition have occurred on an unprecedented scale across the globe. We can now sequence the genome, or assay the human transcriptome or metabolome at relatively low cost. Rich, multidimensional data resources are accumulating in large population biobanks linked to electronic health records. Such resources hold the promise of solving previously intractable questions and offer great potential to understand the biology of healthy pregnancy and of adverse pregnancy outcomes, with the ultimate aim of improving outcomes for all women and babies. To date, these resources have made it very easy to generate associations, e.g. between genetic, nutritional or microbial factors and pregnancy outcomes. However, separating mere associations from key causal mechanisms and pathways remains challenging. By bringing together researchers and clinicians from a range of disciplines to share their methodologies and approaches, this Keystone meeting will be poised to capitalize on the growing body of data, to truly understand mechanisms that will be crucial to maternal-fetal biology and medicine. With its diverse organizing committee, and by holding joint sessions with the 'Infections in Pregnancy' meeting, this meeting will bring together groups of investigators, who would not normally have an opportunity to meet. This will catalyze new ideas for future collaborations and research directions. Goals of this keystone meeting are to: (i) highlight research that is moving the field from association to mechanism, especially in the light of growing data availability (ii) catalyze opportunities for sharing of expertise and experience from multiple approaches and disciplines (iii) enable junior researchers to present and engage with the full range of attendees and participate in discussions