The objective of the study was to examine moods and adjustment through the transition to parenthood as an issue affecting the couple; to examine not only the postpartum but also the pregnancy experience and to explore how each partner's experiences interact with those of the other. A longitudinal repeated measures design was utilized with 327 healthy couples with a first-time pregnancy who were from Melbourne, Victoria in 1995-98. Each partner was interviewed on four occasions: mid- and late pregnancy, early postpartum and 4 months postnatally. Twenty per cent of mothers and 12% of fathers were significantly distressed at mid-pregnancy (Time 1) and this persisted until the early postpartum (Time 3) phase. Young age (particularly in women), negative mood, poor relationship functioning, gender role stress (particularly performance failure regarding work and sex in males) and low social support predicted distress in mid-pregnancy (Time 1). Negative mood in partner and self, and poor relationship functioning at mid-pregnancy predicted vulnerability to postnatal distress (Time 3 and/or Time 4). The incidence of distress in couples during mid- and late pregnancy is of concern and highlights the importance of considering the total transition to parenthood, not only the onset of postnatal distress. The analyses of predictors of postnatal distress from prenatal variables suggest that a 'contagion of distress' may operate in some couples. The standard management provided for couples experiencing pregnancy may be inadequate for many couples. These findings suggest that it is important to consider the mood and relationship quality of both partners and to offer intervention services as early as possible to offset possible progression into postnatal depression.