To explore factors contributing to maternity blues, a longitudinal study was carried out on a group of 111 women who received obstetric care at Yamagata University Hospital from November 1994 to August 1995. Cases of maternity blues were found using Stein's Self-Rating Maternity Blues Scale. Mother-child relationships in the women's childhood were assessed using the Parental Bonding Instrument (PBI). Of the 111 women, 17 (15.3%) developed maternity blues during the first postpartum month. The PBI revealed that these depressed women appeared to be cared for less sufficiently in their own childhood than the non-depressed women. As revealed in interviews, they also seemed to receive less support from their families during pregnancy. These findings suggest that maternity blues may be related to insufficient maternal care in childhood, as well as to poor family support during pregnancy.