Abstract According to the WHO guidelines, to counteract the excessive weight gain during pregnancy and to mitigate the increase in oxidative stress (OS) which naturally increases during pregnancy, a healthy lifestyle and a correct diet are crucial as preventive measures to promote health. The MaNu project was conceived precisely to control these factors through dietary counselling. We expect that pregnant women who voluntarily undergo an educational program consisting of specific and accurate dietary advice will be able to emphasize weight control and contain the increase in OS. Our randomized controlled trial (RCT) has a parallel group design and takes place in the Obstetrics and Clinical Nutrition Departments of Michele and Pietro Ferrero Hospital (Verduno, north-western Italy), where physiological pregnant women are enrolled between 12-17 gestational weeks (GWs). The educational intervention takes place between 12-24 GWs. Dietary habits were collected with a questionnaire and urine samples were analysed to quantify the OS using 15-F2t-isoprostane, malondialdehyde and total antioxidant power. The descriptive analyses are based on paired t-tests. Preliminary analyses on 76 women who completed two out of three time points (T0 and T1) indicate that, of women who received the intervention, 35% experienced excessive weight gain (based on guidelines), compared to 39% shown by controls. Following the counselling, the 15-F2t-isoprostane decreased significantly (mean T0=5.1 ng/ml vs. mean T1=3.5 ng/ml, p = 0.02). Concerning nutrient intake, a statistically significant reduction in sugar consumption has been found in the intervention group (mean T0=92.2 g vs. mean T1=83.3 g, p = 0.03). Conversely, no correlations have been detected between OS and the main pro and anti-oxidant macronutrients. Although promising, our findings need further verification since the RCT is still ongoing, and it is imperative to attain the anticipated sample size before drawing any definitive conclusions. Key messages • Dietary counselling during pregnancy should be implemented as a preventive strategy used to counteract potential pregnancy complications and ensure the well-being of both the mother and the baby. • Healthy diet is essential to control the increase in oxidative stress levels during pregnancy and to prevent excessive weight gain, factors that can lead to the onset of pregnancy complications.