Statistical analysis
Patient characteristics are described as proportions for categorical variables and as means and standard deviations for continuous variables. Significance between study groups was assessed by the Chi square test and Fisher’s exact test for categorical variables, t-test and the Mann-Whitney U test, were used as appropriate in relation to cohort distribution. We further divided the whole study cohort into two groups: hemoglobin <11g/dL and ≥11g/dL. A logistic regression analysis was performed to underline independent determinants associated with hemoglobin levels <11g/dL. The model included variables with a potential association with hemoglobin level, age, BMI, smoking status, parity, gestational age at delivery and the period evaluated with respect to the COVID-19 pandemic. A 2-sided P-value < 0.05 indicated statistical significance. The data were analyzed using Software Package for Statistics and Simulation (IBM SPSS version 24, IBM Corp, Armonk, NY).