Statistical analysis
According the concentration of serum ferritin, pregnant women were
classified into two groups (ID group and Normal group). Statistical
analysis was performed using the Statistical Product and Service
Solutions software (SPSS, version 24.0, IBM SPSS Statistics, USA) and
the R Programming Language (R, version 4.0.4, Ross Ihaka,Robert
Gentleman). Kolmogolov-Smirnov and Shapiro-Wilk tests were used to
analyze data distribution normality. All the subjects showed skewed
distribution. Thus, each group of statistics were described with medians
and percentile values. Then, nonparametric Mann-Whitney U test was used
to compare the differences between the two groups. Spearman’s rank
correlation test was used to estimate the relationship between serum
ferritin and thyroid heroines, hemoglobin, and thyroid heroines
separately. The factors of iron nutritional status and thyroid heroines
were used to analyze the canonical correlation to extract principal
features through the correlation between two sets of variables to
further explore the relationship between iron nutritional status and
thyroid heroines. Elastic network regression was used to explore their
specific relationship. The result was considered as statistically
significant difference when the 2-tailed P-value was < 0.05.