Fig. 1

Flowchart of the study design, population, and experiment. A Flowchart of volunteer recruitment and grouping. B The cohort of 79 MCDA twin pregnancies was divided into two groups based on discordance of fetal birth weight. The number of samples in each twin group is listed in the table for metabolomics, ultrasound results and follow-up survey. TTTS, twin to twin transfusion syndrome; TRAP, twin reversed arterial perfusion; TAPS, twin anemia-polycythemia sequence; sFGR, selective fetal growth restriction; MCDA, normal monochorionic diamniotic twins; FT, first trimester, ST, second trimester, TT, third trimester; CP, cord plasma