Background Midwifery continuity of care models for women at low and mixed risk of complications have been shown to improve women’s experiences of care. However, there is limited research on care experiences among women at increased risk of preterm birth. We aimed to explore the experiences of care among women with risk factors for preterm birth participating in a pilot trial (POPPIE) of a midwifery continuity of care model which included a specialist obstetric clinic. Methods A total of 334 pregnant women identified at increased risk of preterm birth were randomly allocated to either midwifery continuity of care (POPPIE group) or standard maternity care. Women in both groups were followed up at six-to-eight weeks postpartum and were invited to complete a postnatal survey either online or by post. An equal status exploratory sequential mixed method design was chosen to collect and analyse the quantitative postnatal survey data and qualitative interviews data. The postnatal survey included measures of social support, trust, perceptions of safety, quality of care, control during childbirth, bonding and quality of life. Categorical data were analysed with chi-squared tests and continuous data were analysed with t-tests and/or Mann-Whitney U test to measure differences in measures scores among groups. The qualitative interview data were subjected to a thematic framework analysis. Data triangulation brought quantitative and qualitative data together at the interpretation stage. Findings A total of 166 women completed the survey and 30 women were interviewed (90 and 16 in POPPIE group; 76 and 14 in standard group). We found survey respondents in the POPPIE group, compared to respondents in the standard group, were significantly more likely to report greater trust in midwives (Mann-Whitney U, p<0.0001), greater perceptions of safety during the antenatal care (t-test, p = 0.0138), have a particular midwife to contact when they needed during their pregnancy (t-test, p<0.0001) and the postnatal period (chi-squared, p<0.0001). They reported increased involvement in decisions regarding antenatal, intrapartum and postnatal care (t-test, p = 0.002; p = 0.008; p = 0.006 respectively); and greater postnatal support and advice about: feeding the baby (chi-squared, p<0.0001), handling, settling and looking after the baby (chi-squared, p<0.0001), baby’s health and progress (chi-squared, p = 0.039), their own health and recovery (chi-squared, p = 0.006) and who to contact about any emotional changes (chi-squared, p = 0.005). There were no significant differences between groups in the reporting of perceptions of safety during birth and the postnatal period, concerns raised during labour and birth taken seriously, being left alone during childbirth at a time of worries, control during labour, bonding, social support, and physical and mental health related quality of life after birth. Results from qualitative interviews provided insight and depth into many of these findings, with women in the POPPIE group reporting more positive experiences of bonding towards their babies and more positive physical health postnatally. Conclusions Compared with standard maternity care, women at increased risk of PTB who received midwifery continuity of care were more likely to report increased perceptions of trust, safety and quality of care. Trial registration ISRCTN (Number: 37733900); UK CRN (ID: 31951).