Few studies have investigated longitudinal trajectories of child socioemotional and behavioural development in relation to maternal prenatal mental health exposure or taken into consideration of the potential buffering effects of psychological intervention during pregnancy. Using data from 1135 mother–child dyads from the EDEN cohort from the general French population, Group-based trajectory modelling was used to model trajectories of behavioural and emotional characteristics measured at four timepoints via a parent-administered Strengths and Difficulties Questionnaire. Using propensity scores and inverse probability weighting to account for confounding factors, multinomial logistic regressions were used to quantify the associations with maternal symptoms of prenatal depression and anxiety. Stratified analyses were conducted by reporting psychologist and psychiatrist consultations during pregnancy. Compared to those without psychological problems, children of mothers with comorbid anxiety and depression retained a higher probability of following high and intermediate trajectories of emotional problems and a high trajectory of conduct problems throughout childhood. This increased risk was not present in the children of mothers who sought support through a prenatal psychologist or psychiatrist consultation. This article adds to a body of evidence underlining the importance of mental health care for expecting mothers.