AbstractBackground:Depression is frequently seen among pregnant women. This is called antenatal depression (AND).Aim:Our aim was to identify clusters of AND and its core symptoms.Methods:The Patient Health Questionnaire-9 (PHQ-9), Pregnancy-Unique Quantification of Emesis and Nausea (PUQE-24), and Nausea and Vomiting of Pregnancy Quality of Life Questionnaire (NVP-QOL) were distributed to 382 pregnant women with a gestational age of 10 to 13 weeks who were attending antenatal clinics. The two PHQ-9 subscale scores were entered into a 2-step cluster analysis. The PHQ-9 items’ capacity to identify AND were examined in terms of the area under curve (AUC) of a receiver operating characteristic (ROC) analysis. The selected symptom items were examined for their diagnostic capability in terms of the graded response model (GRM) in the item response theory (IRT) analysis.Results:Three clusters emerged. Cluster 3 scored highly in the scores of the two PHQ-9 subscales and the two emesis scales. In the ROC, five items showed an AUC > 0.80. The GRM identified four items with high information: ‘loss of interest’, ‘depressed mood’, ‘self-esteem’, and ‘poor concentration’.Conclusions:The core symptoms of antenatal depression were four non-somatic symptoms; particularly, ‘depressed mood’ and ‘loss of interest’. AND did not exist alone, but was accompanied by nausea and vomiting. Hence, we propose a new category: emesis–depression complex among pregnant women.