Breastfeeding can improve health and survival, diminish economic losses and avoid perpetuation of generational health inequality gradients {Bartick:2016dz, Rollins:2016ke, Pérez-Escamilla:2016wb, Victora:2016tx, Sacker:2013uq} . Mothers have learned the message and many initiate breastfeeding but duration rates still fall short of recommendations {Victora:2016tx}. Poorly trained healthcare providers (HPs) and absence of collaboration with the community contribute to undesired early breastfeeding cessation {Odom:2013bv, Stuebe:2014ea, Vila-Candel:2018hf, Garner:2015ef, Wagner:2013gv}. But access to lactation support has been associated with improved breastfeeding rates {Ray: 2018kv}.

Breastfeeding support services (BSS) that offer clinical care at the individual level and opportunities for professional training may help fill this gap in care and are being successfully formalized in some countries {Rosen-Carole:2018iz}. Most of these BSSs are private experiences, probably because meshing a BSS within a public national healthcare system (PNHS) which generally suffers from rigid structures, scarce resources and high resistance to innovation can be challenging. However, the public healthcare system might add to providing equitable access to it for all families, including the most vulnerable by offering structured breastfeeding support (McVicar, 2015).

, . It opened in November 2013 and was called "Unidad de Lactancia Dr. Peset" . it was the first of its characteristics in Spain.  Five years after its implementation it has been assessed with two main aims: 1. To verify the effectiveness of this intervention (does it work?) and 2. To determine the factors that influence its success and sustainability in order to gain direction for improving the project  (what components make it effective? what components interfere with its effectiveness? Are there threats to its sustainability?)