Abstract: The aim of present investigation was to study the relationship between mothers` distress and fetal growth. In this correlational study, 110 pregnant women selected randomly and completed Depression Anxiety Stress Scale (DASS) before ultrasound measurement of fetus. The results of structural equation model have shown that the overall model has been accepted (χ2 = 36.4, df = 24, p>0.05). In fact, by increasing mothers` stress and anxiety, the fetus heart rate was increased and it decreased the height, weight, head circumference and width and femur length of fetus. Therefore, one of the environmental variables that have negative effect on the fetus growth is mother distress, because it can stimulate the fetal autonomic nervous system through the mediating of heart rate.