PurposeThis study aimed to investigate the association between simple markers in fetal abdominal plane, intra-abdominal umbilical venous diameter (D-IUV) and abdominal circumference (AC) discordance at 15-20 weeks' gestation, and adverse pregnancy outcomes in monochorionic diamniotic (MCDA) twins.MethodsWe performed a retrospective analysis of MCDA twins with two live fetuses examined at 15-20 weeks from Jun 2020 to Dec 2021 at Beijing Obstetrics and Gynecology Hospital. Measurement of fetal AC and D-IUV was performed according to standard protocols. Twin pregnancies with major fetal structural anomalies, chromosomal abnormalities, miscarriage, and twin reversed arterial perfusion sequence were excluded. D-IUV and AC discordance in MCDA twins with an adverse pregnancy outcome was compared with a normal pregnancy outcome. Furthermore, the performance of D-IUV and AC discordance in predicting adverse pregnancy outcomes in MCDA twins was assessed.ResultsA total of 105 women with MCDA twin pregnancies were enrolled, contributing 179 visits. Adverse pregnancy outcomes occurred in 33.3% (35/105) of cases in our study. The intra-observer and inter-observer intraclass correlation coefficient (ICC) of both AC and D-IUV were very good or excellent. There was no statistical difference in AC and D-IUV discordance (%) between 15-16, 17-18, and 19-20 weeks (chi(2) = 3.928, P = 0.140; chi(2) = 2.840, P = 0.242). Both AC and D-IUV discordance were greater in twins with adverse pregnancy outcomes than that in twins with normal pregnancy outcome at each pregnancy periods. Both AC discordance (OR 1.2, 95% CI 1.1-1.3) and D-IUV discordance (OR 1.2, 95% CI 1.1-1.2) were associated with adverse pregnancy outcomes. The AUC for predicting adverse pregnancy outcomes by AC discordance was 0.75 (95% CI 0.68-0.83), with a sensitivity of 58.7% (95% CI 51.9-64.5) and a specificity of 86.2% (95% CI 81.7-88.4). The AUC for predicting adverse pregnancy outcomes by D-IUV was 0.78 (95% CI 0.70-0.86), with sensitivity and specificity of 65.1% (95% CI 58.1-70.3) and 86.2% (95% CI 81.7-88.4), respectively.ConclusionsThe AC discordance and D-IUV discordance could predict adverse pregnancy outcomes in MCDA twins. When these simple markers occurred, intensive surveillance was recommended.
