We investigated whether structured maternal lifestyle interventions based on Mediterranean diet or stress reduction influence fetal-infant neurodevelopment detected by detailed fetal neurosonography and Ages and Stages Questionnaires 3rd edition (ASQ) at 12months old. This was a secondary analysis of a randomized clinical trial (2017-2020) including 1,221 singleton pregnancies at high-risk for small-for-gestational age. Participants were randomized into three groups at 19-23 weeks' gestation: Mediterranean diet intervention, stress reduction program or usual care. A detailed neurosonography was performed on 881 participants at mean(SD) 33.4(1.1) weeks' gestation. Neurosonographic measurements were done offline. ASQ was performed on 276 infants at one year of corrected age. Biparietal diameter were similar among study groups. Mediterranean diet group fetuses had deeper insula [26.80(1.68) vs. 26.63(1.75), mm, p=0.02] and longer corpus callosum [42.98 (2.44) vs. 42.62(2.27), mm, p=0.04], with lower rate of suboptimal score infants in ASQ problem-solving domain (6.2% vs. 16.3%, p=0.03); Stress reduction group fetuses had deeper insula [26.90(1.75) vs. 26.63(1.75), mm, p=0.04] and lower rates of suboptimal score infants in ASQ fine motor domain (4.3% vs. 12.8%, p=0.04), compared to usual care group fetuses. Maternal structured intervention during pregnancy of the trial has the potential to modify offspring's neurodevelopment.