Measuring maternal mental health using the Dutch Four-Dimensional Symptom Questionnaire (4DSQ): Pregnancy-related item bias across the perinatal period

pregnant and postpartum women responded differently to the 4DSQ than the women in the comparison group up until 13 weeks post partum. Pregnancy-related item bias lead to overestimation of distress and underestimation of somatization and anxiety. The depression scale was free of bias. The 4DSQ is a valid tool for case-finding and assessment of psychological conditions in the perinatal period, provided cut-off points are adapted up until 13 weeks post partum. Validation of generic questionnaires is recommended before using them in the perinatal period.