Objective:To investigate the risk factors of birth weight discordance in dichorionic diamniotic (DCDA) twins.Methods:This study retrospectively analyzed 1 757 cases of DCDA twin pregnancies from 11 Chinese hospitals from January 1, 2014, to December 31, 2017. Birth weight discordance was defined as ≥ 20% difference between the twins. All cases were divided into two groups: the concordant group ( n=1 520) and discordant group ( n=237). General information was compared and the high-risk factors of birth weight discordance were analyzed. Mann-Whitney U test, Chi-square test or Fisher's exact test, and logistic regression analysis were used as statistical methods. Results:Compared with the concordant group, the discordant group showed a higher incidence of hypertensive disorders of pregnancy [24.5% (58/237) vs 12.8% (194/1 520), χ2=22.882, P<0.05], fetal structural malformations [4.2% (10/237) vs 1.0% (15/1 520), χ2=15.160, P<0.05], fetal distress [6.3% (15/237) vs 1.4% (21/1 520), χ2=22.602, P<0.05], umbilical cord abnormalities [3.8% (9/237) vs 1.2% (18/1 520), χ2=7.607, P<0.05] and abnormal placental cord insertion [3.8% (9/237) vs 1.4% (21/1 520), χ2=34.904, P<0.05], but lower incidence of premature rupture of membranes [11.0% (26/237) vs 16.5% (250/1 520), χ2=4.645, P=0.034]. Logistic regression analysis showed that the independent risk factors of birth weight discordance in DCDA twins were hypertensive disorders of pregnancy ( OR=2.258, 95% CI: 1.620-3.184, P<0.001), fetal structural malformations ( OR=4.268, 95% CI: 1.892-9.631, P<0.001), umbilical cord abnormalities ( OR=2.889, 95% CI: 1.245-6.705, P=0.014) and abnormal placental cord insertion ( OR=2.318, 95% CI: 1.012-5.311, P=0.047). Conclusions:Hypertensive disorders of pregnancy, fetal structural malformations, umbilical cord abnormalities and abnormal placental cord insertion may be the risk factors of birth weight discordance in DCDA twins.