Systematic approaches to information giving and decision support for women with previous caesarean sections are needed.

To evaluate decision support within a ‘real‐world’ shared decision‐making model.

A pragmatic comparative effectiveness randomised trial in the Positive Birth After Caesarean Clinic. Women with one previous caesarean and singleton pregnancy <25 weeks were randomly allocated to standard Positive Birth After Caesarean care, or standard Positive Birth After Caesarean care plus a decision aid booklet. Main outcome measure was mode of birth, with secondary measures of knowledge, decisional conflict, birth choice, adherence to birth choice, perception of decision support, and satisfaction. Results Of 297 participants, rate of attempted vaginal birth after caesarean increased and was similar for both groups (61% vs 57%, P = 0.5). Knowledge scores increased more for women in the additional decision aid group (2.0 vs 1.6 points, P = 0.2). Decisional conflict score reduction was similar between groups (P = 0.5). Women initially unsure of their birth preference who received the additional decision aid had greater reduction in decisional conflict score (P = 0.04) and were more likely to plan vaginal birth after caesarean (49% vs 33%, P = 0.2). Adherence to birth choice and birth satisfaction was similar between groups. Women in the additional decision aid group rated their decision support tool higher (P < 0.01). Conclusions In a ‘real world' shared decision‐making model, an additional decision aid conferred some benefits in factors associated with preparation for shared decision‐making. Decision aids may provide particular benefit for women who are initially unsure and need assistance in the deliberation phase.