Fig. 2

a Distribution of the difference between USG- and LMP-based GA. The x-axis is the difference between USG and LMP-based GA in weeks, and the y-axis is the number of observations. b BA analysis to evaluate the bias between USG and LMP-based GA. The x-axis is mean of Hadlock and LMP-based GA in weeks, and the y-axis is the difference between Hadlock and LMP-based GA in weeks. Regression line with 95% CI is shown. c Comparison of individual-level classification of preterm birth by Hadlock- and LMP-based methods. Green (term birth for both), red (preterm birth for both), blue (term birth for LMP but preterm birth for Hadlock) and purple (term for Hadlock but preterm for LMP)