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).