Table 3.

Use of the model COM-B to identify the components of the intervention

	Components COM-B	What needs to happen for the target behaviour to occur?	Is there a need for change?
CAPABILITY (C)	Physical capability	Have the physical capacity to read the PtDA.	No. The reading of the PtDA doesn’t require special physical skills.
	Psychological capability	Know how to use the PtDA.	Yes. In another study, more than half of the participants did not did not know of any PtDAs, therefore did not know how they are used.
OPPORTUNITY (O)	Physical opportunity	The PtDA is available.	Yes. For the tool to be used, it must be available.
	Social opportunity	Have the opportunity to see other women use the PtDA.	Yes. As the PtDA is not available yet, pregnant women have not heard about it or had the opportunity to see anyone else using it.
MOTIVATION (M)	Reflective motivation	Believes that using the PtDA could be useful.	Yes. In another study, more than half of the participants did not know of any PtDAs, therefore did not know it could be useful.
	Automatic motivation	Have established a routine and a habit to use the PtDA.	No. It is a one-time behaviour so there is no need for it to become habitual.
	Diagnosis of COM-B components	Psychological capability, physical opportunity, social opportunity and reflective motivation are components needed in an intervention to increase women’s intention to use the PtDA.