Single umbilical artery--right or left? does it matter?

Current Perspectives of Prenatal Sonography of Umbilical Cord Morphology

The umbilical cord constitutes a continuation of the fetal cardiovascular system anatomically bridging between the placenta and the fetus. This structure, critical in human development, enables mobility of the developing fetus within the gestational sac in contrast to the placenta, which is anchored to the uterine wall. The umbilical cord is protected by unique, robust anatomical features, which include: length of the umbilical cord, Wharton’s jelly, two umbilical arteries, coiling, and suspension in amniotic fluid. These features all contribute to protect and buffer this essential structure from potential detrimental twisting, shearing, torsion, and compression forces throughout gestation, and specifically during labor and delivery. The arterial components of the umbilical cord are further protected by the presence of Hyrtl’s anastomosis between the two respective umbilical arteries. Abnormalities of the umbilical cord are uncommon yet include excessively long or short cords, hyper or hypocoiling, cysts, single umbilical artery, supernumerary vessels, rarely an absent umbilical cord, stricture, furcate and velamentous insertions (including vasa previa), umbilical vein and arterial thrombosis, umbilical artery aneurysm, hematomas, and tumors (including hemangioma angiomyxoma and teratoma). This commentary will address current perspectives of prenatal sonography of the umbilical cord, including structural anomalies and the potential impact of future imaging technologies.

Prenatal diagnosis of single umbilical artery and postpartum outcome

OBJECTIVES

To investigate the incidence of the single umbilical artery (SUA) malformation and postpartum outcomes in a retrospective analysis of 781 fetuses.

MATERIALS AND METHODS

This retrospective analysis included 781 pregnant women carrying singleton fetuses diagnosed with SUA at Gansu Provincial Maternal and Child-care Hospital between 2013 and 2019. Detailed data on maternal and fetal characteristics and postpartum outcomes were obtained.

RESULTS

In total, 624 (79.9 %) fetuses were diagnosed with isolated SUA and 157 (20.1 %) fetuses had SUA together with other structural and/or chromosome abnormalities. The highest incidence of malformation was found in the urinary system, followed by the cardiovascular system and digestive system. The incidence of SUA was 59.1 % on the right side and 40.9 % on the left side. Fetuses with SUA and other abnormalities tended to have a lower mean birth weight (3061 g vs 3201 g, p < 0.01), but no difference in the rate of preterm delivery was noted.

CONCLUSIONS

After a diagnosis of SUA, structural observation of the fetus is required. The urinary, cardiovascular and digestive systems should be the focus of observation. If relevant malformations are found, then genetic testing must be performed. With isolated SUA, dynamic monitoring of biological indicators is recommended for lower birth weight, but genetic testing is not recommended.

Four "fine" messages from four kinds of "fine" forgotten ligaments of the anterior abdominal wall: have you heard their voices?

On the posterior aspect of the anterior abdominal wall, there are four kinds of "fine" ligaments. They are: the round ligament of the liver, median umbilical ligament (UL), a pair of medial ULs, and a pair of lateral ULs. Four of them (the round ligament, median UL, and paired medial ULs) meet at the umbilicus because they originate from the contents of the umbilical cord. The round ligament of the liver originates from the umbilical vein, the medial ULs from the umbilical arteries, and the median UL from the urachus. These structures help radiologists identify right-sided round ligament (RSRL) (a rare, but surgically important normal variant), as well as to differentiate groin hernias. The ligaments can be involved in inflammation; moreover, tumors can arise from them. Unique symptoms such as umbilical discharge and/or location of pathologies relating to their embryology are important in diagnosing their pathologies. In this article, we comprehensively review the anatomy, embryology, and pathology of the "fine" abdominal ligaments and highlight representative cases with emphasis on clinical significance.

An Absent Right Umbilical Artery Versus Absent Lt and the Prognostic Implications for the Fetus

A single umbilical artery (SUA) is one of the most common malformations in a fetus, with approximately a 1% occurrence rate. A retrospective study of 108 fetuses with a SUA was done to determine if the laterality of the SUA made a difference in fetal prognosis. An absent right umbilical artery was found in 42 (38.9%) of cases and an absent left umbilical artery in 66 (61.1%) cases. When correlated with fetal outcome, there was a closer association between an absent right umbilical artery with genitourinary anomalies, cardiac defects, and chromosomal abnormalities. There was a nine times greater likelihood (95% confidence interval of a 3 to 27 times greater probability) of a fetal anomaly with an absent right umbilical artery than with an absent left umbilical artery.

Prenatal sonographic diagnosis of single umbilical artery: Emphasis on the absent side and its relation to associated anomalies

OBJECTIVE

To determine the absent side of a single umbilical artery (SUA) and to evaluate whether associated anomalies are related to the side of the missing artery in a Taiwanese population.

MATERIALS AND METHODS

We retrospectively studied SUA fetuses from our computer database of fetal ultrasound in a tertiary medical center in Southern Taiwan. All cases were diagnosed as SUA prenatally using conventional scanners of two- and three-dimensional (2D and 3D, respectively) ultrasound, as well as color, power, and high-definition Doppler. The absent side of UA and associated anomalies were analyzed.

RESULTS

From September 2006 to November 2011, 31 fetuses with SUA were diagnosed prenatally by ultrasound and all were enrolled for this series. The incidence was estimated to be 1:556 (0.18% = 31/17,086). The mean maternal age was 29.2 years (range, 15-36 years) and the mean fetal age was 30.0 weeks of gestation (range 18-36 weeks). Notably, the left-absent UA was detected in 16/31 (52%) fetuses, compared with the right-absent UA in 15/31 (48%) cases. In addition, congenital anomalies were noted prenatally in 2/16 (13%) fetuses with left-absent UA and in 3/15 (20%) fetuses with right-absent UA.

CONCLUSION

In SUA fetuses, the absence of UA appears to occur equally at each side. Moreover, this study showed no significant difference between either side of missing UA and associated anomalies after statistical examination.

Single umbilical artery: Does side matter?

INTRODUCTION

The aim of this study was to determine if laterality of an absent umbilical artery (AUA) is associated with specific sonographic findings, chromosomal defects or postpartum birth defects.

MATERIALS AND METHODS

In this retrospective cohort study, ultrasound reports and medical records of patients who received an obstetric ultrasound at the University of Iowa Hospitals and Clinics with an identified laterality of the AUA from 1989 to 2007 (n = 405) were reviewed. Rates of sonographic abnormalities between fetuses with a right versus left AUA were compared using Fisher's exact test. Adjustments for confounding were made using logistic regression modeling. The significance level was set at 0.05.

RESULTS

Right AUAs on ultrasound demonstrate higher unadjusted rates of ultrasound abnormalities with a higher percentage of fetuses with >1 additional abnormality (51.1 vs. 37.0%; p = 0.0043). The left AUA group had a significantly higher percentage of isolated AUA (63.0 vs. 48.8%; p = 0.004). In a multivariate analysis, a sonographic right AUA was significantly associated with gastrointestinal (GI) and genitourinary (GU) abnormalities. No other ultrasonographic and umbilical artery Doppler abnormalities, chromosomal defects or postpartum birth defects were significantly associated with a specific laterality of the AUA.

DISCUSSION

Our study identified a significant association between a right AUA and concomitant fetal GI and GU abnormalities. Contrary to previous reports, we conclude that laterality of the AUA may prove to be an easily identified early marker of fetal abnormalities.

Isolated single umbilical artery: need for specialist fetal echocardiography?

OBJECTIVE

To examine the association between single umbilical artery (SUA) and cardiac defects and to determine whether patients with SUA require specialist fetal echocardiography.

METHODS

Incidence and type of cardiac defects were determined in fetuses with SUA detected at routine second-trimester ultrasound examination.

RESULTS

A routine second-trimester scan was performed in 46 272 singleton pregnancies at a median gestation of 22 (range, 18-25) weeks and an SUA was diagnosed in 246 (0.5%). Cardiac defects were diagnosed in 16 (6.5%) of these cases, including 10 (4.3%) in a subgroup of 233 with no other defects and in six (46.2%) of the 13 with multiple defects. In 11 (68.8%) of the 16 cases with cardiac defects the condition was readily diagnosable by evaluating the standard four-chamber view and the views of the great arteries. In the remaining cases there was left persistent superior vena cava or small ventricular septal defect, where prenatal diagnosis may not be important because they are not associated with adverse outcome.

CONCLUSION

Although SUA is associated with an increased incidence of cardiac defects it may not be necessary to refer such patients for specialist fetal echocardiography because the defects are detectable by evaluating standard cardiac views that should be part of the routine second-trimester scan.

Single umbilical artery risk factors and pregnancy outcomes

OBJECTIVE

To identify risk factors for fetuses and neonates with single umbilical artery and isolated single umbilical artery (single umbilical artery in the absence of chromosomal abnormalities and structural abnormalities) and to assess whether there is an increased risk for complications during pregnancy, labor, and delivery, and for perinatal morbidity and mortality.

METHODS

A population-based retrospective cohort analysis of deliveries in Nova Scotia, Canada, between 1980 and 2002 was conducted using the Nova Scotia Atlee Perinatal Database. Risk factors and outcomes for single umbilical artery and isolated single umbilical artery pregnancies were compared with three-vessel-cord pregnancies. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each outcome using multiple logistic regression to adjust for confounding factors. Separate models were run for single umbilical artery and isolated single umbilical artery.

RESULTS

There were 203,240 fetuses and neonates available for analysis, with 885 (0.44%) having single umbilical artery and 725 (0.37%) having isolated single umbilical artery. Single umbilical artery fetuses and neonates had a 6.77 times greater risk of congenital anomalies and 15.35 times greater risk of chromosomal abnormalities. The most common congenital anomalies in chromosomally normal fetuses and neonates were genitourinary (6.48%), followed by cardiovascular (6.25%) and musculoskeletal (5.44%). For isolated single umbilical artery, placental abnormalities (OR 3.63, 95% CI 3.01-4.39), hydramnios (OR 2.80, 95% CI 1.42-5.49), and amniocentesis (OR 2.52, 95% CI 1.82-3.51) occurred more frequently than with three vessel cords. Neonates with single umbilical artery and isolated single umbilical artery had increased rates of prematurity, growth restriction, and adverse neonatal outcomes.

CONCLUSION

Fetuses and neonates with single umbilical artery and isolated single umbilical artery are at increased risk for adverse outcomes. Identification of single umbilical artery is important for prenatal diagnosis of congenital anomalies and aneuploidy. Increased surveillance with isolated single umbilical artery may improve pregnancy outcomes.

LEVEL OF EVIDENCE

II.

Isolated single umbilical artery and fetal karyotype

OBJECTIVE

To determine the need for fetal karyotyping in cases of an isolated single umbilical artery (SUA) identified during the second-trimester routine anomaly scan.

METHODS

All patients booked for antenatal care and delivery in our hospital are offered two ultrasound scans in pregnancy, one at 11-13 weeks' gestation as part of screening for chromosomal defects and another at 20-23 weeks for detailed fetal examination. In addition we examine patients referred from other hospitals because of suspected fetal abnormalities during their routine second-trimester scan. We performed a search of the database to retrieve all cases with an SUA and reviewed the ultrasound findings, fetal karyotype and pregnancy outcome.

RESULTS

There were 643 cases with SUA, including 424 (65.9%) where the condition was isolated, 133 (20.7%) with one major fetal defect and 86 (13.4%) with multiple defects. The incidence of chromosomal abnormalities was 0% in the isolated SUA group, 3.7% in those with one defect and 50.7% in those with multiple defects. The commonest chromosomal abnormalities were trisomy 18, trisomy 13 and triploidy, which together accounted for 82.9% of cases.

CONCLUSION

The finding of an SUA should prompt the sonographer to search for fetal defects and if these are found the risk for chromosomal abnormalities is increased. In cases of apparently isolated SUA there is no evidence of increased risk of chromosomal abnormalities.

Single umbilical artery in fetopathological investigations

Single umbilical artery (SUA) is a relatively common malformation that may call attention to the possibility of associated malformations (often chromosome aberrations). The current study aimed at surveying malformations associated with SUA on the basis of fetopathological investigations, analyzing the role of history, summarizing the clinically important factors emerging together with this malformation. In this study, we processed the details of 204 cases in which SUA was confirmed fetopathologically after miscarriage or induced abortion between 1990 and 2007. In our sample, SUA occurred in 7.38% of the cases. The history was positive in almost 30% of the cases. The majority of the cases had a positive obstetric and the minority of them a positive genetic history. The highest association of SUA with other malformations was found for craniospinal ones, but an association with cardiovascular malformations should also be mentioned. Regarding the individual types of malformation, SUA was most commonly associated with hydrocephalus, but Potter's sequence, trisomy 21, and atrioventricular septal defect also reached a higher rate in associated SUA. Previously published articles dealing with associated malformations found that urogenital malformations were most commonly associated with SUA. 'Itemizing' the different non-chromosomal malformations in association with SUA, we found that hydrocephalus, Potter's sequence, and atrioventricular septal defect were the most frequent malformations, while in earlier studies, the association with non-chromosomal malformations such as vertebral malformations, imperforated anus, cheilognathopalatoschisis, and renal agenesis occurred more frequently than usual.

The value of single umbilical artery in the prediction of fetal aneuploidy: findings in 12,672 pregnant women

OBJECTIVES

To assess the risk of the association of single umbilical artery and aneuploidies.

METHODS

In a general unselected obstetric population of 12,672 singleton pregnant women from January 1998 to December 2002, we detected 61 fetuses (prevalence, 0.48%) with single umbilical artery (SUA) on prenatal ultrasound at 16 to 23 menstrual weeks.

RESULTS

Among the 61 fetuses with 2-vessel cord, 39 (64%) had SUA as an isolated finding, and 22 (36%) had additional findings, either minor or major. One (2.56%) of the 39 fetuses with SUA as an isolated finding had aneuploidy (trisomy 21 at maternal age of 32 years), whereas 5 (41.6%) of the 12 fetuses with SUA concomitant with major anomalies were aneuploid. None of the 10 fetuses with SUA and minor anomalies had aneuploidy. Among the 12,611 women with 3-vessel cord, we instead found 8 cases of trisomy 21 (0.06%), 1 case of translocation 14-21 (0.007%), 5 cases of trisomy 18 (0.04%), 1 case of trisomy 13 (0.007%), 1 case of 47,XXX (0.007%), and 2 cases of monosomy X (0.01%).

CONCLUSIONS

In an unselected population, second trimester sonographic detection of SUA and major fetal anomalies indicate increased risk for fetal aneuploidy. However, even if this study is based on a large population, the only 1 case of trisomy 21 among the fetuses with SUA as an isolated finding is not sufficient to draw a conclusion, and larger studies are needed to confirm or infirm this single case.

Single umbilical artery and its siding in the second trimester of pregnancy: relation to chromosomal defects

OBJECTIVES

To determine the possible association between single umbilical artery (SUA) in the second trimester of pregnancy and the incidence of chromosomal abnormalities. To determine whether the presence of chromosomal defects in fetuses with SUA is related to the side of the missing artery.

METHODS

Color flow imaging of the fetal pelvis was used to determine the number of umbilical arteries in 2147 fetuses immediately before amniocentesis for karyotyping in the second trimester of pregnancy.

RESULTS

SUA was diagnosed in 102/2147 (4.8%) cases. The left umbilical artery was absent in 60/102 (58.8%) fetuses, compared with the 42/102 (41.2%) for the right artery. The rate of chromosome abnormalities was significantly higher among fetuses with SUA than among those with 2 umbilical arteries (19/102 or 18.6% versus 109/2045 or 5.3%; OR = 4.1, 95% CI 2.3-7.1, p < 0.0001). Among fetuses with SUA, there was no significant difference in the rate of chromosome abnormalities between those with absence of the left versus the right artery (11/60 or 18.3% versus 8/42 or 19.0%, p = 0.93). There was an SUA in 5/39 (12.8%) cases with trisomy 21, 8/16 (50%) with trisomy 18, 1/4 (25%) with trisomy 13 and 5/69 (7.2%) with other chromosomal defects. There were no chromosome abnormalities in fetuses where a single umbilical artery was an isolated sonographic finding. All fetuses with SUA and chromosomal defects had associated abnormalities detected by ultrasound.

CONCLUSION

A single umbilical artery (SUA) in the second trimester of pregnancy has a high association with trisomy 18, 13, 21 and other chromosomal defects, but all chromosomally abnormal fetuses had associated malformations detected by ultrasound. The absence of the left artery is more frequent than the absence of the right artery. The association with chromosomal abnormalities seems to be equal on each side.

Perinatal results following the prenatal ultrasound diagnosis of single umbilical artery

OBJECTIVE

To study the perinatal results in our population, following the prenatal ultrasound diagnosis of a single umbilical artery (SUA), as this alteration is associated with fetal malformations, chromosomal abnormality, and poor perinatal results.

MATERIALS AND METHODS

A retrospective review of all obstetric ultrasounds carried out between October 2000 and December 2003 in our service, obtaining the postnatal results of the fetuses diagnosed with an SUA.

RESULTS

From a total of 5,987 pregnant patients examined by ultrasound scan at 20th week, an SUA was found in 40 cases, representing an incidence of 0.7%. Of these, 84.6% were normal pregnancies at birth and 15.4% presented other malformations and/or chromosomal abnormalities. No aneuploidy was found in pregnancies where there were no other associated findings in the ultrasound scan at 20 weeks. All cases with serious congenital malformations accompanying the SUA were diagnosed prenatally. There was a 5% of perinatal mortality rate among our fetuses with SUA, which represents a mortality rate 10 times greater than the overall rate among our patients.

CONCLUSIONS

The ultrasound discovery of an SUA implies the meticulous search for other associated malformations, and in the absence of these, the risk of a chromosomal abnormality is very low, unless it is a high-risk patient. However, the growth and wellbeing of the fetus must be carefully monitored in the last 3 months, although the ultrasound scan does not show any other associated alterations.

Early detection of fetal structural abnormalities

Most published data on the detection of fetal anomalies at 11-14 weeks are from specialized centres with considerable experience in fetal anomaly scanning. However, there is still limited information on the feasibility and limitations of the screening of these anomalies compared with the now classical mid-gestation screening. This review indicates that overall, the detection rate of fetal anomalies at 11-14 weeks is 44% compared with 74% by the mid-pregnancy scan. Major abnormalities of the fetal head, abdominal wall and urinary tract, and of the umbilical cord and placenta, can be reliably detected at 10-11 weeks of gestation. Detection of other anomalies such as spina bifida, diaphragmatic hernia or heart defects is limited before 13 weeks of gestation. So far it cannot be stated that routine first trimester screening can be used on a large scale to evaluate the fetal spine and heart in the general population. In particular, in screening for congenital heart defects, the ability to perform a full cardiac examination increases from 20% at 11 weeks to 92% at 13 weeks. The early prenatal diagnosis of these anomalies may be improved by screening at 13-14 weeks rather than during the first trimester.

Controversial ultrasound findings

This article has reviewed a few of the more controversial findings in the field of obstetric ultrasound. For each one evidence-based strategies for the management of affected pregnancies have been suggested, derived from what the authors believe is the best information available. In some cases, this information is very limited, which can make counseling these patients extremely difficult. Some physicians find using specific likelihood ratios helpful in these complex discussions. An example of the relative likelihood ratios for several markers of trisomy 21 is illustrated in Table 10. Although the management of each of the findings discussed in this article is different, a few generalizations can be made. To begin with, the detection of any abnormal finding on ultrasound should prompt an immediate detailed ultrasound evaluation of the fetus by someone experienced in the diagnosis of fetal anomalies. If there is more than one abnormal finding on ultrasound, if the patient is over the age of 35, or if the multiple marker screen is abnormal, an amniocentesis to rule out aneuploidy should be recommended. Of the six ultrasound findings reviewed here, the authors believe that only echogenic bowel as an isolated finding confers a high enough risk of aneuploidy to recommend an amniocentesis in a low-risk patient. The other findings in isolation in a low-risk patient seem to confer only a modest increased risk of aneuploidy, if any, and this risk is certainly less than the risk of unintended loss from amniocentesis. Wherever possible, modifiers of this risk, such as maternal age, history, and first and second multiple marker screening, should be used to define more clearly the true risk of aneuploidy. As obstetric ultrasound moves forward, particularly into the uncharted waters of clinical use of three- and four-dimensional ultrasound, one can expect a whole new crop of ultrasound findings with uncertain clinical significance. Clinicians are well advised to await well-designed studies to determine the clinical significance of these findings before altering clinical care.

Single umbilical artery at 11-14 weeks' gestation: relation to chromosomal defects

OBJECTIVE

To determine the possible association between single umbilical artery (SUA) at 11-14 weeks of gestation and the incidence of chromosomal abnormalities.

METHODS

Color flow imaging of the fetal pelvis was used to determine the number of umbilical arteries in 717 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks' gestation.

RESULTS

Single umbilical artery (SUA) was diagnosed in 21/634 (3.3%) chromosomally normal fetuses, in 5/44 (11.4%) with trisomy 21, 14/18 (77.8%) with trisomy 18 and 2/21 (9.5%) with other chromosomal defects. In the chromosomally normal group there was no significant difference in median fetal crown-rump length or nuchal translucency (NT) between those with a single and those with two umbilical arteries. In the 42 fetuses with SUA the expected number of cases of trisomy 21, estimated on the basis of maternal age, gestational age and fetal NT, was 4.7, which was not significantly different from the observed 5. The corresponding numbers for trisomy 18 were 2.0 for expected and 14 for observed (Fisher's exact test P = 0.0016).

CONCLUSION

A SUA at 11-14 weeks' gestation has a high association with trisomy 18 and other chromosomal defects.

Prenatal diagnosis of single umbilical artery: determination of the absent side, associated anomalies, Doppler findings and perinatal outcome

OBJECTIVE

To determine the absent side of a single umbilical artery and its association with malformations and abnormal karyotypes.

METHODS

We prospectively studied 102 fetuses from 13 to 39 weeks of gestational age with a prenatally identified single umbilical artery. The absent side, pregnancy data, Doppler findings and the perinatal outcome were reviewed.

RESULTS

(1) The left umbilical artery was absent in 71 (69.6%) and the right in 31 (30.4%) fetuses; (2) Single umbilical artery as an isolated finding occurred in 59 (57.8%) pregnancies and was not associated with aneuploidy. The mean gestational age at delivery in this group was 38.4 weeks and the mean birth weight was 3047 g. Six (10.2%) fetuses were small for gestational age, all of them with normal umbilical and uterine Doppler findings; and (3) Chromosomal abnormalities were diagnosed in 10 of 43 fetuses with single umbilical artery and congenital malformations. In nine of 10 fetuses with aneuploidy the left umbilical artery was not developed. Absence of the left artery occurred in 21 of 33 fetuses with sonographic anomalies and normal karyotype. Pathologic Doppler measurements of the umbilical artery were found in only one case of nonchromosomal abnormality.

CONCLUSION

Our data suggest that in fetuses with single umbilical artery the absence of the left artery is more frequent than the absence of the right artery. The association with additional malformations seems to be equal on each side.