Abstract
Objectives: Single umbilical artery (SUA) is considered the most common abnormality of the umbilical artery. The objective of the study was to evaluate the perinatal prognosis of fetuses with SUA and to describe the associated malformations. The significance of the study is represented by examining whether our findings are in correlation with data already described.
Methods: We performed a prospective cohort study on singleton pregnancies complicated with SUA. The study population was composed of women with singleton pregnancies who were examined at the Department of Obstetrics and Gynecology of the Târgu Mures County Emergency Clinical Hospital between 2012 and 2021.
Results: The incidence of SUA in the study population was 0.48%. C-section was performed in 40 cases with SUA and in 5258 cases with no SUA (RR:1.56, P<0.05.) From the total number of 2249 premature deliveries, 23 newborns were diagnosed with SUA (RR:2.12, P<0.05.) From the total number of 869 deliveries with low birth weight (LBW) newborns, 13 were associated with SUA (RR: 3.12, P<0.05.) There were 206 pregnancies noted with antenatal fetal demise after 24 weeks of gestation, and only 2 of them were with SUA (RR:2.01, P>0.05.) Fetal and neonatal malformations were described in 290 cases, and 28 were associated with SUA (R:21.96, P<0.05.) In 57 of 85 cases (67.05%), we found iSUA, and 28 newborns (32.95%) had minor, major, or other associated pathologies. We found two cases of trisomy 18 and one case with trisomy 13 associated with SUA. Investigating the malformations associated with SUA, the most common were cardiac and great vessels malformations (12), followed by limb malformations (8), urogenital malformations (7), digestive tract malformations (7), central nervous system malformations (4), and in one case we found cleft palate.
Conclusions: Perinatal prognosis regarding SUA is significantly poorer than in cases without this pathology. One-third of fetuses with SUA were associated with fetal anomalies. The most common pathologies associated with SUA were cardiovascular, limb, urogenital, and digestive system malformations. Our data are similar to those described in other studies; therefore, we conclude, we can implement the general recommendations in our region regarding counselling patients.
The umbilical cord physiologically contains three blood vessels, of which two are arteries and one is a vein. The absence of one of the arteries is considered a fetal malformation and is called single umbilical artery (SUA).1 SUA is considered the most common abnormality of the umbilical artery, its incidence ranging between 0.5%-1%. The single umbilical artery may be an isolated finding, or it may be associated with aneuploidy or other congenital anomalies. When it occurs without any associated abnormality, it is considered an isolated single umbilical artery (iSUA).2
Umbilical cord examination has become an integrated part of routine obstetric ultrasound examination, and the structure of the umbilical cord must be investigated. Prenatal ultrasonographic identification of a SUA is usually performed by investigating the umbilical cord in longitudinal and cross sections. The umbilical arteries can also be identified at the level of the fetal bladder.3 Therefore, when SUA is identified during the first or second trimester, fetal morphology ultrasound focused on certain pathologies is indicated to detect possible associated abnormalities.4
Currently, in Romania there has been no study addressing the incidence of malformations associated with fetuses with a single umbilical artery. Early detection of such a pathology is important, because in these cases increased attention will be paid to the evolution of the fetus in utero and multiple non-invasive prenatal tests will be performed. As regards to the mother, the early diagnosis of a fetal malformation bears an important role in counseling.
The significance of the study is represented by examining whether the incidence of SUA, associated malformations, and perinatal prognostics in our region is in correlation with the data described in other studies. The objective of the study was to evaluate the perinatal prognosis of fetuses with SUA and to describe the associated malformations, compared to newborns without this pathology of the umbilical cord.
Material and Methods
We performed a prospective cohort study to investigate the perinatal conditions of newborns with SUA and to describe the incidence of associated malformations. The study population was composed of women with singleton pregnancies who were examined at the Department of Obstetrics and Gynecology of the Târgu Mureș County Emergency Clinical Hospital between 2012 and 2021. We analyzed the distribution of newborns regarding the type of delivery, gestational age at birth, birth weight, antenatal fetal demise after 24 weeks of pregnancy, and incidence of genetic syndromes and malformations. The absence of one umbilical artery was diagnosed by prenatal ultrasound in the majority of the cases, while a few cases were diagnosed after delivery. Data recording, processing, and statistical analysis were performed using Microsoft Excel 2016. The significance value (P) used was 0.05.
Results
Analyzing the births of the past 10 years in our department, we identified 85 pregnancies complicated with SUA out of a total number of 17,553 deliveries; therefore, the incidence of this pathology in the study population was 0.48%. Of newborns, 59.2% were female, and 40.8% were male; in 65.8% of cases, the left umbilical artery was missing. In 40 cases with SUA C-section was performed, and C-section was performed in 5258 cases with no SUA (RR:1.56, P<0.05). From the total number of 2,249 premature deliveries, 23 newborns were diagnosed with SUA (RR:2.12, P<0.05).
The incidence of Low Birth Weight (LBW) after adjusting the gestational age in the SUA group was 14.92%. From the total number of 869 deliveries with LBW newborns, 13 were associated with SUA. RR: 3.12, P<0.05. There were 206 pregnancies noted with antenatal fetal demise after 24 weeks of gestation, and only two of them were with SUA (RR:2.01, P>0.05). Fetal and neonatal malformations were described in 290 cases, and 28 were associated with SUA (RR:21.96, P<0.05). In 57 out of 85 cases (67.05%), we found iSUA, and 28 newborns (32.95%) had minor, major, or other associated pathologies. We found two cases of trisomy 18 and one case with trisomy 13 associated with SUA.
Investigating the malformations associated with SUA, the most common were cardiovascular malformations (12), followed by limb malformations (8), urogenital malformations (7), digestive tract malformations (7), and central nervous system malformations (4). In one case, we found cleft palate and cleft lip. The malformations are presented in Table 1.
Malformations associated to Single Umbilical Artery
Discussion
Meta-analysis performed by Hyeong Ju Kim et al5 provided a systematic review of the association between iSUA presence and various perinatal conditions. The results of this meta-analysis suggests that iSUA is associated with a significant increase in perinatal conditions such as LBW, premature birth, pregnancy-induced hypertension, long-term care in neonatal intensive care units, and perinatal mortality, which is in correlation with our findings.
Our results were similar to those described by Geipel et al,6 assuming that absent left umbilical artery (69.6%) was more common than the absent right (30.4%). Urogenital and cardiovascular malformations were the most common abnormalities, while gastrointestinal lesions were less common.6 Regarding newborn malformations, the most common were cardiovascular malformations, followed by limb malformations, urogenital malformations, digestive tract malformations, central nervous system malformations, and in one case cleft palate and lip. Compared to the data described in the literature, these results correspond to those described by Ebbing et al7 in a populational study performed on 918,933 pregnant women, that showed 0.65% (n = 5949) of the population had at least one malformation compared to 10.9% (n = 464) of cases with SUA. A particularly strong association was observed between SUA and atresia of upper or lower gastrointestinal stenosis, followed by renal agenesis, diaphragmatic hernia, and limb abnormalities. The risk for different congenital heart defects was increased in pregnancies with SUA. There was an association between SUA and microcephaly, congenital hydrocephalus and other congenital malformations of the brain and spinal cord. There were strong associations between SUA and trisomies 13 and 18 and a weaker association with trisomy 21. Of fetuses with trisomy 18, 48% were aborted and 53% of those with trisomy 13 were aborted before 22 weeks of pregnancy.7
After analyzing the results, we obtained an incidence of pregnancies complicated with SUA of 0.48%, which is very close to the incidence described in the meta-analysis by Yajuan et al.2 We observed a statistically significant association between fetuses with SUA and the incidence of C-section delivery, preterm birth, and LBW. These findings are similar to the data described in the literature.1,8,9 From the total of 85 cases, 57 (67.05%) were iSUA and 28 (32.95%) had associated fetal malformations. These data correspond to those described in the literature by Tulek et al.4
Limitations of this study are represented by the small number of cases examined and the absence of Romanian national data regarding the pregnancies with SUA.
Conclusions
The incidence of complicated pregnancies with a single umbilical artery is 0.48% in the studied population. In cases with SUA, the umbilical artery is predominantly missing on the left side. C-section delivery, incidence of preterm birth, LBW, and associated fetal malformations are significantly higher among pregnancies with SUA, but were not a risk for antenatal fetal demise. We can therefore conclude that the perinatal prognosis regarding SUA is significantly poorer than in cases without this pathology.
One of the most important prognostic factors of the fetuses with SUA is the association of other fetal malformations. One-third of fetuses with SUA were associated with fetal anomalies. The most common pathologies associated with SUA were cardiovascular, limb, urogenital, and digestive system malformations. SUA, once diagnosed, preferably at the end of the first trimester, requires a very thorough examination of fetal morphology in the second trimester. Also non-invasive prenatal testing is indicated for genetic diagnostics. Our data are similar to those described in other studies; therefore, we conclude we can implement the general recommendations in our region regarding counselling patients.
Footnotes
Disclosures: The authors have reported no financial support or personal or financial conflicts of interest related to this work.
- Received June 10, 2022.
- Revision received November 11, 2023.
- Accepted December 11, 2023.
References
- 1.↵Murphy-Kaulbeck L, Dodds L, Joseph KS, Van den Hof M. Single umbilical artery risk factors and pregnancy outcomes. Obstet Gynecol. 2010;116(4):843-850. doi:10.1097/AOG.0b013e3181f0bc08
- 2.↵Xu Y, Ren L, Zhai S, Association Between Isolated Single Umbilical Artery and Perinatal Outcomes: A Meta-Analysis. Med Sci Monit. 2016;22:1451-1459. Published 2016 Apr 30. doi:10.12659/msm.897324
- 3.↵Sepulveda W, Peek MJ, Hassan J, Hollingsworth J. Umbilical vein to artery ratio in fetuses with single umbilical artery. Ultrasound Obstet Gynecol. 1996;8(1):23-26. doi:10.1046/j.1469-0705.1996.08010023.x.
- 4.↵Tülek F, Kahraman A, Taşkın S, Özkavukçu E, Söylemez F. Determination of risk factors and perinatal outcomes of singleton pregnancies complicated by isolated single umbilical artery in Turkish population. J Turk Ger Gynecol Assoc. 2015;16(1):21-24. doi:10.5152/jtgga.2015.15115.
- 5.↵Kim HJ, Kim JH, Chay DB, Park JH, Kim MA. Association of isolated single umbilical artery with perinatal outcomes: Systemic review and meta-analysis. Obstet Gynecol Sci. 2017;60(3):266-273. doi:10.5468/ogs.2017.60.3.266.
- 6.↵Geipel A, Germer U, Welp T, Schwinger E, Gembruch U. Prenatal diagnosis of single umbilical artery: determination of the absent side, associated anomalies, Doppler findings and perinatal outcome. Ultrasound Obstet Gynecol. 2000;15(2):114-117. doi:10.1046/j.1469-0705.2000.00055.x
- 7.↵Ebbing C, Kessler J, Moster D, Rasmussen S. Single umbilical artery and risk of congenital malformation: population-based study in Norway. Ultrasound Obstet Gynecol. 2020;55(4):510-515. doi:10.1002/uog.20359
- 8.↵Burshtein S, Levy A, Holcberg G, Zlotnik A, Sheiner E. Is single umbilical artery an independent risk factor for perinatal mortality?. Arch Gynecol Obstet. 2011;283(2):191-194. doi:10.1007/s00404-009-1326-3
- 9.↵Leung AKC, Robson WL. Single umbilical artery. A report of 159 cases. Am J Dis Child. 1989;143(1):108-111. doi:10.1001/archpedi.1989.02150130118030.
