What is a dyad?

A breastfeeding woman and her infant are often referred to as a dyad by breastfeeding support professionals. A dyad is defined as

• "1. Something that consists of two parts; 2. a group of two people, which is the smallest possible social group" (Cambridge Dictonary online), or

• "Two individuals maintaining a sociologically significant relationship" (Merriam Webster Dictionary online).

Neuroprotective Developmental Care (NDC or the Possums programs) aims to avoid technical terms or scientific jargon unless the terms improve accuracy in inter-professional communication. In NDC we might sometimes refer to breastfeeding mother-infant pairs, since this what the word 'dyad' actually means.

But the term dyad characterises the mother and her infant as one unit made up of two separate parts. Although this term has been a step in the right direction, it is now outdated because it fails to accurately represent the complex physiological and biobehavioural interrelatedness of a mother and her breastfeeding infant. The term dyad fails to represent the the way the single biological system of the mother and baby comprises myriad interacting factors and feedback loops (physiological, biobehavioural, psychological, sociocultural). It also fails to represent the broader contexts in which any complex adaptive system operates, and which interact with and profoundly shape the system.

When we need to be at our most accurate and scientific in NDC, we refer to the single biological system of the mother and her infant as a complex adapative system or CAS, not a dyad. Otherwise, we refer to a mother-baby pair.

What is a complex adaptive system (CAS)?

The whole of a CAS arises out of dynamically co-evolving and self-organising parts. Multiple biobehavioural, psychosociocultural, and physiological complex adaptive systems are nested within each other, influencing each other.

• The term mother-infant CAS signals the complexity of the interactions between the many complex adaptive systems of the mother and baby (physiological, psychological, and biobehavioural), which sit inside other familial, sociocultural and environmental systems.

• The mother-baby CAS is an interconnected ecosystem, formed from interdependent immune, metabolic, thermoregulatory, microbiome, psychoneurobiological and nutritional systems.

• In the mother-baby CAS, the function of the whole cannot be explained by the behaviour of any single component.

• A small perturbation in the mother-baby CAS may have amplified and unpredictable effects over time (‘butterfly effect’).

• The mother-baby CAS is remarkably resilient because of the myriad feedback loops which interact to self-organise and stabilise a CAS when faced with perturbations.

• Health, behaviour, or mood problems emerge when myriad interacting feedback loops fail to stabilise the mother-baby CAS.

• Multi-lateral strategies are typically required to help stabilise the mother-baby CAS when problems emerge.

• Uni-lateral or simplistic interventions typically result in unexpected (and often unhelpful) outcomes when inserted in a complex adaptive system.

Resources

• You can find out about how a mother (or loving carer) and her baby form a single biological system here.

• You can find out more about resilience, the butterfly effect, and being a biological system as you breastfeed your baby here.

• You can find out why breastfeeding is a symphony of biological systems here.

• You can find out about the One Factor Fallacy here.

Selected references

Braithwaite J, Churruca K, Long JC. When complexity science meets implementation science: a theoretical and empirical analysis of systems change. BMC Medicine. 2018;16:63.

Douglas PS, Hill PS, Brodribb W. The unsettled baby: how complexity science helps. Arch Dis Child. 2011;96:793-797.

Greenhalgh T. Complexity theory and family medicine: a new symbiosis. Prim Care. 2010;10(2):19.

Greenhalgh T, Papoutsi C. Studying complexity in health services research: desperately seeking an overdue paradigm shift. BMC Medicine. 2018;16:95.

Guillen-Morales DdJ, Cruz-Cortes I, Sosa-Velazco TA, Aquino-Dominguez AS. The mother-infant symbiosis: a novel perspective on the newborn's role in protecting maternal breast health. Hygiene. 2025;5(46):https://doi.org/10.3390/hygiene5040046.

Paley J. The appropriation of complexity theory in health care. J Health Serv Res Policy. 2010;15(1):59-61.

Reed JE, Howe C, Doyle C, Bell D. Simple rules for evidence translation in complex systems: a qualitative study. BMC Medicine. 2018;16:92.

Wolpert M, Rutter H. Using flawed, uncertain, proximate and sparse (FUPS) data in the context of complexity: learning from the case of child mental health. BMC Medicine. 2018;16:82.