The intervention was an eight-session P-IPTG, which consisted of four sessions in pregnancy and four in postpartum. All participants replied to the measures at four waves from baseline to one year postpartum. The outcome variables were within-group and between-group changes in depression, social support, dyadic adjustment, interpersonal relationship satisfaction, and mother-infant bonding.

The participants of control group reply questionnaires for four times.

Interpersonal psychotherapy (IPT) was developed by Stuart and O'Hara (1995). It addresses four domains of conflict. The intervention is an eight-session P-IPTG, which consisted of four sessions in pregnancy and four in postpartum.

The Edinburgh Postnatal Depression Scale (EPDS, Cox et al., 1987) was used to assess depressive symptoms. It consists of ten Likert-type items with 0 to 3 points, with higher scores indicating more depressive symptoms over the past week. Following the previous study (Su et al., 2007), we used higher than 12 to define participants with significant depressive tendencies.

The Dyadic Adjustment Scale (DAS, Spanier, 1976) assessed women's perceived quality of either married or unmarried couple relationship. The scale consists of 32 items, primarily scored in a 6-point scale (27 items). It measures four factors: dyadic consensus, dyadic satisfaction, dyadic cohesion, and affectionate expression. Higher scores indicate better dyadic adjustment in respective aspects.

The Social Network Interaction System Questionnaire (SNISQ, Lay & Liu, 1996) was used to evaluate perceptions of social support from partners, original families, and in-laws. The SNISQ consists of nine Likert-type items with 1 to 4 points, with higher scores indicating better- perceived support from specific individuals.

Chan et al. (2002) used the Satisfaction with Interpersonal Relationships Scale (SWIRS,) to assess women's satisfaction with their relationships with partners and mothers-in-law over the past few weeks. We expanded the scale to include ratings of relationships with fathers, mothers, and fathers-in-law, resulting in five items. The SWIRS is a Likert-type item with 1 to 7 points, with higher scores indicating greater satisfaction with the relationship.