The cognitive model of OCD has suggested that people with OCD have an inflated sense of responsibility which drives them to repeatedly check to avoid being responsible for harm to other people or themselves. Research into this model has suggested that responsibility beliefs cause OC symptoms. However, there is limited empirical research exploring the developmental origins of responsibility beliefs. This study sought to build on existing literature that has suggested that attachment style and perceived parenting are involved in the development of OC symptoms, through responsibility beliefs. Specifically this study aimed to explore whether responsibility beliefs mediated the relationship between a) perceived parenting and OC symptoms and b) attachment style and OC symptoms. This study aimed to build on previous literature by using a sample of pregnant women. It has been hypothesised that pregnancy is a trigger for OCD due to the increase of responsibility at this time. A cross-sectional questionnaire design was used with a sample of 106 non-clinical pregnant women. The Parental Bonding Instrument was used to measure perceived parenting, the Experiences in Close Relationships Questionnaire- Revised was used to measure attachment style, the Obsessive Compulsive Inventory was used to measure OC Symptoms, Responsibility/Threat subscale of the Obsessive Beliefs Questionnaire-44 was used to measure responsibility and the Depression, Anxiety and Stress Scale-21 was used as a measure of mood. The current study found that responsibility mediated the relationship between; i) paternal overprotection and OC symptoms, and ii) attachment anxiety and OC symptoms. However, the mediation model did not hold for maternal care, maternal overprotection, paternal care or attachment avoidance. The findings of the current study move towards drawing together the cognitive and attachment theories of OCD. The paper discusses the theoretical and clinical implications of the findings.