Trajectories of maternal depression, anxiety, stress, and child developmental milestones at 24 months

<i>Background</i>: Literature suggests a link between maternal mental health and adverse child developmental outcomes. However, we do not know to what extent this is true in low and middle-income settings, and most studies do not explore mental health longitudinally since birth.<i>Objective</i>: We aimed to assess the association between maternal mental health and early child development outcomes in southern Brazil.<i>Methods</i>: We studied 992 mother-child pairs in a birth cohort from 2019 to 2022. We used standardised instruments to assess maternal depression, anxiety, and distress at different time points during the perinatal period. We used Group Based Trajectory Modelling to create maternal mental health trajectories. We assessed these trajectories associated with the child's social, language, cognitive, and motor development at 24 months using Poisson multiple regression models.<i>Results</i>: Children of mothers with elevated symptoms of depression experienced an 80% [RR = 1.80; 95%CI(1.19-2.71)] increase in language delays, 23% [RR = 1.23; 95%CI(1.01-1.51)] in cognitive delays, and 40% [RR = 1.40; 95%CI(1.07-1.83)] in motor delays. Children of mothers experiencing increasing symptoms of anxiety to moderate levels had 38% [RR = 1.38' 95%CI(1.07-1.82)] more language delays and 20% [RR = 1.20; 95%CI(1.05-1.38)] more cognitive delays. Low subjective distress led to 54% [RR = 1.54; 95%CI(1.15-2.05)] more language delays.<i>Conclusion</i>: Our findings underscore the effect of maternal mental health on child developmental outcomes among this sample in southern Brazil.