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.

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.

Femur and humerus length in trisomy 21 fetuses at 11-14 weeks of gestation.

OBJECTIVE: To determine the value of measuring fetal femur and humerus length at 11-14 weeks of gestation in screening for chromosomal defects. METHODS: Femur and humerus lengths were measured using transabdominal ultrasound in 1018 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks of gestation. In the group of chromosomally normal fetuses, regression analysis was used to determine the association between long bone length and crown-rump length (CRL). Femur and humerus lengths in fetuses with trisomy 21 were compared with those of normal fetuses. RESULTS: The median gestation was 12 (range, 11-14) weeks. The karyotype was normal in 920 fetuses and abnormal in 98, including 65 cases of trisomy 21. In the chromosomally normal group the fetal femur and humerus lengths increased significantly with CRL (femur length = - 6.330 + 0.215 x CRL in mm, r = 0.874, P < 0.0001; humerus length = - 6.240 + 0.220 x CRL in mm, r = 0.871, P < 0.0001). In the Bland-Altman plot the mean difference between paired measurements of femur length was 0.21 mm (95% limits of agreement - 0.52 to 0.48 mm) and of humerus length was 0.23 mm (95% limits of agreement - 0.57 to 0.55 mm). In the trisomy 21 fetuses the median femur and humerus lengths were significantly below the appropriate normal mean for CRL by 0.4 and 0.3 mm, respectively (P = 0.002), but they were below the respective 5th centile of the normal range in only six (9.2%) and three (4.6%) of the cases, respectively. CONCLUSION: At 11-14 weeks of gestation the femur and humerus lengths in trisomy 21 fetuses are significantly reduced but the degree of deviation from normal is too small for these measurements to be useful in screening for trisomy 21.

Tricuspid regurgitation in the diagnosis of chromosomal anomalies in the fetus at 11-14 weeks of gestation.

OBJECTIVE: To analyse patient data to elucidate the apparent association between an abnormal karyotype and tricuspid regurgitation found during fetal echocardiography at early gestations. SETTING: Tertiary referral centre for fetal medicine and cardiology. METHODS: Fetuses between 11 and 14 weeks' gestation were selected for detailed echocardiography. Referral reasons were increased nuchal translucency, a suspected cardiac or extracardiac malformation, and a family history of cardiac malformation. INTERVENTION: The fetus was imaged transabdominally. The four chamber view, outflow tracts, arterial duct, and aortic arch were assessed on cross sectional imaging and colour flow mapping. Pulsed Doppler of the atrioventricular valves was recorded if possible. Subsequently, the fetal karyotype was ascertained by chorionic villous sampling. RESULTS: Pulsed Doppler recording of the tricuspid valve was obtained for 262 fetuses. Tricuspid regurgitation was present in 70 (27%) of these, of whom 58 (83%) proved to have karyotype anomalies. In contrast, 68 (35%) of those without tricuspid regurgitation were found to have karyotype anomalies (95% confidence interval 36% to 59%, p < 0.001). Structural heart defects were detected in 34 of the 58 (59%) with tricuspid regurgitation and in 22 (32%) of those without. The chromosome defect most frequently found to be associated with tricuspid regurgitation was trisomy 21, but all types of karyotypic anomalies were seen in association. CONCLUSION: A careful search for tricuspid regurgitation is an important aspect of the evaluation of the early fetus, as this is frequently a marker for chromosomal defects even in the absence of structural heart disease.