Parents play a significant role in scaffolding how children approach and recover from painful medical procedures.  An important mechanism of successful recovery post-painful procedure is how the parent responds to their child and provides external regulatory support over the early years. Caregivers play a critical role in how children regulate pain-related distress and it fundamentally requires the caregivers themselves to be regulated despite the stressful nature of observing their child in high distress.  Physiological attunement research provides an understanding of how coregulatory dynamics between parent and child emerge early in life and provides insight into how pain-related distress regulation develops. This presentation will present new data on the dynamic process of cardiac attunement between parent and child during toddler vaccinations (12-18 months of age; n=189). Three distinct profiles of caregiver-toddler regulatory attunement, indexed by high-frequency heart rate variability, were discerned using parallel-process growth mixture modelling and will be presented. Follow-up work will also be presented that examines psychosocial predictors of these three distinct profiles, showing that parental worry and infant behavioural distress were related to more adaptive versus maladaptive dyadic regulatory patterns. Results will be discussed in terms of the DIAPR-R 2022 Model (Pillai Riddell et al, 2022).