The perinatal period is characterised by the fundamental status transition of birth. Surrounding this transition is a period of a few months where choices are being made about life and death, where social disparities in morbidity and mortality are magnified, where later life health outcome have their origin, where abundant data is collected, and where bodies are being subjected to medical, legal, and political scrutiny and intervention. Demographers have started to untangle this dense transitional period with a recent push towards studying cohorts as they navigate the challenges surrounding parturition.