Statistical analyses
All study variables will be described as median and range or mean and standard deviation for quantitative variables, and absolute and relative frequencies for categorical variables. A first trimester nutritional score representing the adherence to a healthy diet and lifestyle will be calculated as the sum of 10 questions. Bivariate correlations will be performed to investigate the associations between maternal baseline characteristics and the first trimester nutritional score. A multivariate analysis adjusted for confounding factors including pregestational BMI, age, gestational weight gain, smoking habit, ethnicity, and fetal sex, will be conducted to assess the associations between maternal nutritional status and study outcomes. The relative risk of adverse outcomes (e.g. low birth weight, gestational diabetes, hypertensive disorders and preterm birth) will be calculated in case of low nutritional scores in the nutritional questionnaire, considering a threshold of 6. P -values < 0.05 will be considered statistically significant. Statistical analyses will be performed using SPSS Statistics for Windows, Version 21.0 (IBM Corp. Armonk, New York, NY, USA) and R version 3.2.1 (The R Foundation for Statistical Computing).