The development and initial validation of the Perinatal Intrusions Interpretation Index: A novel scale that measures negative appraisals of infant‐related intrusive thoughts

OBJECTIVES: Unwanted and often distressing intrusive thoughts of infant-related harm are common during the perinatal period and are associated with poorer maternal mental health. The mechanisms linking perinatal intrusive thoughts to mental health remain poorly understood. One proposed avenue is through maladaptive appraisals, yet there currently are no measures capturing perinatal-specific appraisals. The aim of the current study was to develop and validate a novel Perinatal Intrusions Interpretation Index (PIII) to assess negative appraisals related to intrusions of infant-related harm. METHODS: 439 people who were 1-6 months postpartum completed 12 items capturing appraisals of perinatal intrusions and an adapted online version of the Postpartum Intrusions Interview. A second validation sample, N = 142 people ≤ 9 months postpartum, completed the final 10-item PIII. RESULTS: Exploratory and confirmatory factor analyses indicated a three-factor structure of the PIII: (1) inflated responsibility, (2) importance of thoughts and (3) need for control. The total PIII and subscales demonstrated good internal consistency. Higher negative appraisals on the PIII were significantly associated with more frequent and distressing intrusive thoughts of accidental and intentional infant-related harm and more maladaptive behavioural responses to perinatal intrusions. Intrusion type (accidental vs intentional) moderated the relationship between negative appraisals and intrusion frequency and distress and frequency of behavioural responses. CONCLUSIONS: The PIII is a reliable and valid scale to assess negative appraisals of infant-related harm intrusions. Negative appraisals may be a cognitive risk factor for perinatal intrusions to progress from normative to functionally impairing, offering a modifiable target for the prevention and treatment of perinatal anxiety disorders.