Purpose <p>Relationship satisfaction is a key factor in women’s mental health and wellbeing outcomes, however, relationship satisfaction may change in times of stress and uncertainty, such as the perinatal period. While positive romantic relationships during the perinatal period may offer benefits, changes in relationship satisfaction and what may contribute to them longitudinally is not currently well understood.</p> Method <p>One hundred and fifty-seven women in late pregnancy (~ 30 weeks gestation) took part in a longitudinal analysis of relationship satisfaction from pregnancy to five years postpartum, across eight timepoints. The study is a secondary analysis of a randomised controlled trial of sleep and diet intervention. Latent growth modelling was used to examine the trajectory of relationship satisfaction change over time and explore predictors of this trajectory.</p> Results <p>There was a significant decline in relationship satisfaction both during pregnancy and the postpartum. Being of non-White race was associated with overall lower relationship satisfaction (<i>p</i> = 0.004). While being less financially comfortable (<i>p</i> = 0.007), having less than a postgraduate degree (<i>p</i> = 0.049), and older age (<i>p</i> = 0.026) were associated with steeper decrease in relationship satisfaction during the postpartum.</p> Conclusion <p>This study demonstrates that relationship satisfaction declines from pregnancy to five years postpartum in a sample of Australian mothers. Minority race, financial comfortability, education level and age may influence the magnitude of this trajectory. These findings highlight a need to better support couples during this challenging time, not just through pregnancy and birth, but also through early childhood.</p>