With the mature application of assisted reproductive technologies, the incidence of multiple pregnancies has increased dramatically, and complications including premature labor, fetal malformations, preeclampsia, and gestational diabetes have also increased. Perinatal prognosis and fetal survival quality can be improved through fetal reduction. Selective fetal reduction in the first trimester may result in a better prognosis than selective fetal reduction in the second trimester, suggesting that early assessment of pregnancy outcome in early pregnancy will provide a significant improvement in maternal and fetal prognosis.

To explore the relationship of ultrasonographic soft markers in early pregnancy and twin-specific markers with the pregnancy outcome of double chorionic double amniotic sac twins (DCDA) .

Pregnant women and fetuses with DCDA twin pregnancies in early pregnancy (11-13⁺⁶ weeks) attending the Department of Ultrasound Medicine of Longgang District Maternity&Child Healthcare Hospital of Shenzhen City from May 2018 to May 2022 were retrospectively selected for the study. The detection rates of ultrasonographic soft markers and twin-specific markers in DCDA twin pregnancies in early pregnancy and their association with adverse pregnancy outcomes. Ultrasonographic soft markers included thickened nuchal translucency (NT), choroid plexus cyst, nasal bone dysplasia, ventricular punctate strong echo, tricuspid regurgitation, absence or inversion of ductus venosus A wave, intestinal echo enhancement, mild dilatation of the renal pelvis, single umbilical artery and right subclavian artery vagus. Twin-specific markers included differences in twin crown-rump length (CRL), twin NT, and twin umbilical cord insertion (UCI). Adverse pregnancy outcomes included miscarriage, stillbirth, neonatal death, structural abnormalities, and genetic abnormalities, with the addition of positive weight gain (≥25% difference in twin weights) as a specific adverse pregnancy outcome. Logistic regression analysis was used to explore the correlation of ultrasonographic soft markers and twin-specific markers of DCDA twin pregnancies in early pregnancy with adverse fetal pregnancy outcomes.

Finally, 418 cases pregnant women of DCDA twin pregnancies in the first trimester were included, of which 342 cases (81.82%) had normal pregnancy outcomes and 76 cases (18.18%) had adverse pregnancy outcomes. The total detection rate of positive ultrasonographic soft markers in twin pregnancies in the first trimester was 10.53% (53/418) ; a total of 61 ultrasonographic soft markers were detected in 53 fetuses with positive ultrasonographic soft markers, and the top three detection rates were NT thickening in 6.94% (29/418), choroid plexus cyst in 2.39% (10/418) and nasal bone dysplasia in 1.67% (7/418). The incidence rate of adverse pregnancy outcomes for fetuses with positive ultrasonographic soft markers was 30.19% (16/53), and the incidence rate of adverse pregnancy outcomes for fetuses with negative ultrasonographic soft markers was 16.44% (60/365) ; the incidence rate of adverse pregnancy outcomes for fetuses with positive ultrasonographic soft markers in the first trimester was higher than fetuses with negative ultrasonographic soft markers (χ²=5.882, P=0.015). Binary Logistic regression analysis results showed that a twin CRL difference≥15% was a risk factor for adverse pregnancy outcomes in twin pregnancy (OR=9.955, 95%CI=1.882-52.662, P=0.007), and a positive twin UCI difference was a risk factor for positive fetal weight in twin pregnancy (OR=3.733, 95%CI=1.300-10.720, P=0.014). The total detection rate of positive twin-specific markers in fetuses with twin pregnancies in early pregnancy was 27.27% (114/418), including 12 cases with a twin CRL difference≥15% and a negative twin UCI difference, 100 cases with a twin CRL difference<15% and a positive twin UCI difference, and 2 cases with a twin CRL difference≥15% and a positive twin UCI difference. The total detection rate of fetuses with ultrasonographic soft markers but positive twin-specific markers in early pregnancy was 25.12% (105/418). The incidence of adverse pregnancy outcomes and positive weight gain among fetuses with negative ultrasound soft markers but positive twin-specific markers was 27.6% (29/105), and the incidence of adverse pregnancy outcomes among fetuses with negative ultrasound soft markers alone was 16.4% (60/365). The incidence of adverse pregnancy outcomes and positive weight gain in fetuses with negative ultrasonographic soft markers but positive twin-specific markers in early pregnancy was higher than the incidence of adverse pregnancy outcomes in fetuses with negative ultrasonographic soft markers alone (χ²=6.641, P=0.010). The total detection rate of positive ultrasonographic soft markers combined with positive twin-specific markers in fetuses with twin pregnancies in early pregnancy was 2.15% (9/418), and the incidence of adverse pregnancy outcomes combined with positive weight gain in fetuses with positive ultrasonographic soft markers combined with positive twin-specific markers was 44.4% (4/9), and the incidence of adverse pregnancy outcomes in fetuses with positive ultrasonographic soft markers alone was 30.2% (16/53). There was no statistically significant difference in the incidence of adverse pregnancy outcomes combined with positive weight gain in fetuses with positive ultrasonographic soft markers combined with positive twin-specific markers compared with the incidence of adverse pregnancy outcomes in fetuses with positive ultrasonographic soft markers alone (χ²=0.212, P=0.645). The results of multivariate Logistic regression analysis showed that NT thickening (OR=2.576, 95%CI=1.146-5.791, P=0.022), twin-fetal CRL difference≥15% (OR=13.167, 95%CI=3.595-48.229, P<0.001), and positive twin-fetal UCI difference (OR=2.369, 95%CI=1.049-5.348, P=0.038) were risk factors for adverse fetal pregnancy outcome and positive weight gain in DCDA twin pregnancies in early pregnancy.

NT thickening, twin-fetal CRL difference≥15%, and positive twin-fetal UCI difference may be risk factors for adverse fetal pregnancy outcomes and positive weight gain in DCDA twin pregnancies in early pregnancy. The fetus with positive ultrasonographic soft markers or positive twin-specific markers should be vigilant, and comprehensive evaluation and close follow-up should be carried out.