Pregnancy provides motivation for women to improve their diets and increase their physical activity. Opportunistic brief interventions delivered as part of routine primary care have produced improvements in patients' health behaviour. Consequently, there have been calls for midwives to use contacts during pregnancy in this way. This study explored the experiences of pregnant women and research midwives/nurses of a brief intervention called Healthy Conversation Skills (HCS) being delivered as part of a randomised control trial, assessing the acceptability and feasibility of including this intervention in routine maternity care. Three research questions were addressed using mixed methods to produce four datasets: face-to-face interviews with participants, a focus group with the HCS-trained midwives/nurses, case reports of participants receiving HCS and audio-recordings of mid-pregnancy telephone calls to the women which produced midwife/nurse HCS competency scores. Midwives/nurses used their HCS to support women to make plans for change and set goals. Women welcomed the opportunity to address their own health and well-being as distinct from that of their baby. Midwives/nurses were competent in using the skills and saw healthy conversations as an effective means of raising issues of diet and physical activity. Recent extension of maternity appointment times provides ideal opportunities to incorporate a brief intervention to support behaviour change. Incorporating HCS training into midwifery education and continuing professional development would facilitate this. HCS is a scalable, brief intervention with the potential to improve the diets and physical activity levels of women during pregnancy, and hence the health of themselves and their babies. © 2019 The Authors. Maternal & Child Nutrition published by John Wiley & Sons, Ltd.