Background: The concept of well-being is multi-faceted by encompassing both positive and negative emotions and satisfaction with life. Measuring both positive and negative thoughts and emotions is highly relevant in maternity care that aims to optimise a woman's experience of pregnancy and childbirth, focussing on positive aspects of health and well-being, not just the prevention of ill health. Yet our understanding of well-being in pregnancy and childbirth is limited as research to date has focussed on negative aspects such as stress, anxiety or depression. The primary aim of this study is to describe the psychometric properties of a newly developed Well-being in Pregnancy (WiP) questionnaire.Methods: A cohort study of 318 women attending hospital antenatal clinics in Belfast completed a questionnaire including three general well-being measures (not pregnancy specific) and the newly developed WiP questionnaire. The psychometric properties of the questionnaire were analysed using correlations to explore the relationship between the WiP questionnaire with the generic well-being measures administered at the same time and exploratory factor analysis was conducted.Results: The overall Cronbach's alpha of the WiP was 0.73. Principal factor analysis was run on the WiP items and two factors were identified, one reflecting positive affect and satisfaction (Cronbach's alpha=0.718) and the other concerns (Cronbach's alpha=0.702). Both the overall WiP score and WiP sub-scale scores displayed significant correlations with the other well-being scales (r=0.235-0.527).Conclusions: Measuring well-being in pregnancy is an important step in understanding the potential physical, psychological and social benefits of pregnancy and in understanding how well-being can be enhanced for women and their families at this important life stage. The initial psychometric data presented for the WiP questionnaire are encouraging. Most importantly, the measure provides an opportunity for women to express positive and negative emotions and thoughts about their pregnancy thus reflecting the whole spectrum of well-being.