Background: Previous research suggests, though not consistently, that maternal psychological distress during pregnancy leads to adverse birth outcomes. We investigated whether maternal psychological distress affects fetal growth during the period of mid-pregnancy until birth.Method Pregnant women (n=6313) reported levels of psychological distress using the Brief Symptom Inventory (anxious and depressive symptoms) and the Family Assessment Device (family stress) at 20.6 weeks pregnancy and had fetal ultrasound measurements in mid-and late pregnancy. Estimated fetal weight was calculated using head circumference, abdominal circumference and femur length.Results In mid-pregnancy, maternal distress was not linked to fetal size. In late pregnancy, however, anxious symptoms were related to fetal size after controlling for potential confounders. Anxious symptoms were also associated with a 37.73 g [95% confidence interval (CI) 69.22 to 6.25, p=0.019] lower birth weight. When we related maternal distress to fetal growth curves using multilevel models, more consistent results emerged. Maternal symptoms of anxiety or depression were associated with impaired fetal weight gain and impaired fetal head and abdominal growth. For example, depressive symptoms reduced fetal weight gain by 2.86 g (95% CI 4.48 to 1.23, p<0.001) per week.Conclusions The study suggests that, starting in mid-pregnancy, fetal growth can be affected by different aspects of maternal distress. In particular, children of prenatally anxious mothers seem to display impaired fetal growth patterns during pregnancy. Future work should address the biological mechanisms underlying the association of maternal distress with fetal development and focus on the effects of reducing psychological distress in pregnancy.