Abstract： Objective:To summarize the ultrasonographic characteristics, genetic etiology, and perinatal prognosis of fetuses with absence of ductus venosus (ADV).Methods:A retrospective study enrolled 84 singleton pregnancies that underwent prenatal ultrasound examination and were diagnosed with fetal ADV at the First Affiliated Hospital of Zhengzhou University from June 2017 to July 2022. Based on prenatal ultrasonographic findings, the cases were divided into isolated ADV group ( n=37), ADV with ultrasound soft markers group ( n=9), and ADV with definite ultrasound abnormalities group ( n=38). According to the gestational age at the initial diagnosis of ADV, they were categorized into early pregnancy group (11-13 weeks of 6 days) with 17 cases, mid-pregnancy group (14-27 weeks of 6 days) with 45 cases, and late pregnancy group (≥28 weeks) with 22 cases. Depending on the direction of blood flow in the intra-abdominal segment of the umbilical vein, they were classified into umbilical vein directly entering the portal sinus group ( n=75), intrahepatic umbilical vein abnormal shunt group ( n=4), and extrahepatic umbilical vein shunt group ( n=5). The clinical characteristics of each group were summarized, and compared using the Chi-square, trend Chi-square tests, Fisher's exact test and Bonferroni correction test. Results:The common ultrasonographic abnormalities in the 84 cases of ADV fetuses were cardiac anomalies (27.4%, 23/84), cystic hygroma (10.7%, 9/84), fetal hydrops (9.5%, 8/84), and body cavity effusion (8.3%, 7/84). The proportions of fetuses with ADV and definite ultrasound abnormalities detected in the early, mid, and late pregnancy were 16/17, 44.4% (20/45), and 9.1% (2/22), respectively, with a higher proportion of definite ultrasound abnormalities associated with earlier detection of ADV ( χ 2trend=27.25, P<0.001). Among them, 21 cases underwent chromosomal karyotyping and/or chromosomal copy number variation sequencing or expanded non-invasive prenatal testing, with five abnormalities detected, including 45,X, trisomy 13, trisomy 22 mosaicism, trisomy 7 mosaicism, and a 14 Mb duplication at 22q12.3q13.33. The neonatal survival (28 days after birth) rates with ADV detected in the early, mid, and late pregnancy gradually increased, at 1/17, 43.9% (18/41), and 90.5% (19/21), respectively ( χ 2trend=27.04, P<0.001). The neonatal survival rates of the isolated ADV group and the group with ultrasound soft markers were higher than that of the group with definite ultrasound abnormalities [93.9% (31/33) and 6/9 vs. 2.7% (1/37), Bonferroni corrected, both P<0.001]. The neonatal survival rates of the umbilical vein directly entering the portal sinus group, intrahepatic umbilical vein abnormal shunt group, and extrahepatic umbilical vein shunt group were 50.0% (35/70), 0/4, and 1/5, respectively, with no statistically significant difference (Fisher's exact test, P=0.105). Conclusions:The earlier the detection of fetal ADV, the more likely it is to be associated with definite ultrasound abnormalities and have lower neonatal survival rates. This highlights the importance of ultrasonographic examination of the fetal ductus venosus. Once ADV is detected, attention should be paid to other potential ultrasound abnormalities, and genetic testing should be completed.