This paper reports on an action research case study of integrated obstetric care in the Netherlands. Efficient and patient-friendly patient flows through integrated care networks are of major societal importance. How to design and develop such inter-organizational patient flows is still a nascent research area. We have shown that a modification of an existing method to support inter-organizational collaboration by system dynamics based group model building (the Renga method (Akkermans 2001)) may be effective in achieving such collaboration. At the time writing, the action research project that this paper reports upon is still ongoing, but so far, perceived results are promising.