Objective: to explore the experiences and practice of midwives in relation to the assessment of maternal postnatal genital tract health. Design: a constructionist grounded theory methodology was employed to guide the research design and processes. Ethical approval was gained from the regional research ethics committee and the research and development committee at the data collection site. Sampling was purposeful and data were collected using narrative style in depth interviews involving 14 midwives. Observations of 15 postnatal assessments involving five midwives and 15 postnatal women were also undertaken. Setting: a small maternity unit providing midwifery care to childbearing women in both the hospital and community setting in the North East of England. Findings: three themes were identified from the data and form the framework of the constructed grounded theory: Methods, Motivators and Modifiers. Within each theme are a number of categories and focused codes. The Methods theme summarises a range of assessment methods used by the midwives, including risk assessment, questioning and clinical observations. The Motivators theme incorporates factors which motivated how, when and why the midwives undertook genital tract assessment and includes verification, personal preferences and sensitive care. The Modifiers theme consists of factors and contexts, which facilitated or inhibited the midwives' ability to negotiate an appropriate approach to assessment including therapeutic relationship, care in context and evolving midwifery knowledge. Conclusions: the findings of this study suggest midwives are aware of a range of assessment methods; however there was less articulation or demonstration of methods pertaining to assessment of uterine health. The motivating and modifying factors highlight midwife, woman and contextual factors, which may enhance and inhibit the midwives clinical reasoning process. The complexity of contemporary midwifery practice is illuminated as these factors conflict and create practice tensions and contradictions for the midwives. Implications include the need to ensure midwives have the knowledge regarding uterine health and the skills, affective abilities, resources and opportunities to engage women in health assessments within the complexity of contemporary practice.