Accuracy of assessment of fetal anomalies using compressed fetal ultrasound video clips

Ultrasound Obstet Gynecol 2001; 18 (Suppl. 1): 11–31

Free Communications FC01: CARDIAC 1 F01 The accuracy and indications of fetal echocardiography in high risk patients: a 4-year clinical experience in an obstetric unit O. Go´mez, B. Puerto, A. Borrell, M. Palacio & V. Cararach Objective: To evaluate the accuracy and assess the indications of fetal echocardiography to diagnose structural heart disease in our high risk population, by an obstetric team. Methodology: Over a 4-year period, a transabdominal echocardiography was performed in 912 high risk pregnancies for congenital heart disease at 18–38 weeks of gestation. In the last 140 cases, an early examination combining either the transvaginal or the transabdominal route at 13–16 weeks was also carried out. Follow up was obtained from neonatal examinations and autopsies. The main indications for referral were: pregestational diabetes mellitus, family risk, increased nuchal translucency, suspected cardiac anomaly at screening ultrasound, women at high risk of chromosomal abnormality reluctant to invasive test, suspected arrhythmia, single umbilical artery, exposure to teratogens, and pregnancies affected by a chromosomal abnormality. Results: There were 79 (8.6%) major congenital heart defects, and most of them were yielded in the group of screening by ultrasound. Seventy of them (88.6%) were diagnosed correctly as abnormal prenatally. Atrioventricular septal defects (21 cases) and hypoplastic left ventricle syndrome (12 cases) were the most prevalent heart anomalies in the fetus. Isolated septal defects and coarctation of the aorta were the most difficult lesions to detect, being the ones with false positive and negative diagnosis. Another four cases of non-significant (1:300 for Down syndrome. The pregnancy outcome, including karyo-type and structural abnormalities, were ascertained for all pregnancies. Results: The DV Doppler was abnormal in 27 (21.8%) pregnancies with an increased first trimester NT-adjusted risk. The outcome was normal in 69 pregnancies (55.6%). Thirty-nine pregnancies (39.5%) were aneuploid and further six pregnancies had adverse outcomes (three unexplained intrauterine deaths, two structural abnormalities and one major cardiac defect). The sensitivity of abnormal DV in this selected population was 51.3% for aneuploidy and 33.3% for adverse outcome. An abnormal DV Doppler increases the risk for aneuploidy by 11.8 (95% CI: 3.3–42.2). Conclusions: The finding of an abnormal DV Doppler signal increases the risk for aneuploidy 12-fold in a pregnancy with an increased NTadjusted risk. Although DV Doppler can be used in addition to NT screening for aneuploidy, the sensitivity of DV Doppler is less than previously reported.

F19 Integrated first and second trimester screening for Down syndrome Y. H. Lam, C. P. Lee, S. Y. Sin, R. Tang, H. S. Wong, S. F. Wong, M. H. Y. Tang & H. H. N. Woo Purposes: It is uncertain whether first trimester nuchal translucency is more effective than the well established second trimester serum screening for fetal Down syndrome or whether their combination works best. We report our data on a large multicenter non-interventional trial in which all subjects underwent both first and second trimester screening to assess their relative efficacy. Methods: All women who attended the obstetric clinic before 15 weeks were recruited. An ultrasound examination was performed at 10–14 weeks to measure the nuchal translucency. The nuchal measurements were not acted upon unless the fetus showed gross features of hydrops fetalis. All women had serum alpha-fetoprotein and human chorionic gonadotrophin assay at 15–20 weeks. The Down syndrome risk assigned by serum screening was disclosed and amniocentesis was offered if this assigned risk was at or >1:250 or if the women were 35 years and older. Efficacy of different combinations of screening were compared. Results: Between January 1997 and August 2000, 17590 women were recruited (19% was 35 years and older). After excluding subjects who miscarried, defaulted the serum test and other reasons, 16237 pregnancies were included in the final analysis. Of these, 35 pregnancies were affected by Down syndrome (2.2 cases per 1000 pregnancies). At a false-positive rate of 5%, the detection rate of Down syndrome by nuchal translucency alone; nuchal translucency þ age; serum human chorionic gonadotrophin, alpha-fetoprotein þ age and nuchal translucency þ human chorionic gonadotrophin þ alpha-fetoprotein þ age

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F20 The affect of image size on nuchal translucency measurement: a report from the FaST study A. G. Edwards, S. F. Mulvey & E. M. Wallace Purpose: To establish whether image size affects nuchal translucency measurement. Methods: A random sample of participants in the FaST study were selected to have additional measurements performed to determine whether image size affects the nuchal translucency measurement. The FaST study is a collaborative research project funded by the Department of Human Services, Victoria Government, and Monash University. This study was established to assess the relative merits of first and second trimester screening for Down syndrome and to thereby determine the optimum screening strategy. Nuchal translucency measurements were performed using an ATL HDI3000 with C5-2 probe with the fetus in a sagittal section and the amnion excluded. Using HD zoom, the image size was adjusted so that the fetus occupied 60, 100 or 200% (head and neck view) of the monitor. Three measurements were taken at each image size, in random order, according to the methods described by the fetal medicine foundation. The ultrasound machine operator was blinded from the measurement values during the examination. Statistical analysis utilizing STATA 6.0 was performed using analysis of variance after log transformation of the nuchal translucency data to produce a normal distribution. Results: Forty-eight women were scanned with nine nuchal translucency measurements performed in each case. All scans were transabdominal. The CRL ranged from 44 to 80 mm and BPD from 15 to 28 mm. The mean NT was 1.5, 1.3, and 1.1 mm at 60, 100 and 200% image sizes, respectively. Analysis of variance with Bonferroni multiple-comparison test revealed statistically significant differences between 60 and 200% (P < 0.0001) and 100 and 200% (P ¼ 0.025) images, but not between the 60 and 100% images (P ¼ 0.057). Conclusion: Image size appears to make a significant difference to the nuchal translucency measurement with an inverse relationship between the fetal image size and the nuchal translucency recorded.

F21 Quality assessment in prospective nuchal translucency screening for Down syndrome in the Copenhagen first trimester study K. Wojdemann, M. Christiansen, K. Sundberg, A.-C. Shalmi & A. Tabor Purpose: To develop and apply a quality control system in a Down syndrome (DS) screening study using nuchal translucency (NT) as interventional marker. Methods: In a prospective DS screening study, the NT was measured in 9236 pregnancies. For quality assessment two models were introduced: (I) image-scoring evaluation of the NT measurements and (II) establishment of the distribution of NT multiple of the medians (MoMs) over time and influence of an intervention. Results: The observer variability in the image-scoring evaluation was high with a kappa value of 0.48 in the overall validation. A revised model showed better interobserver agreement with a kappa value of 0.58; regarding the single criteria the differences were however, still unsatisfactory, i.e. we found highly significant differences for the criteria ‘position of the fetus’ (P ¼ 0.0026) and ‘magnification of the image’ (P ¼ 0.0001). Regarding the distribution of the NT MoMs, the median NT MoM (in groups of 50 fetuses each) stabilized after a short learning phase (representing the practical part of the sonographer’s certification). The intergroup standard deviation decreased from initial 0.100–0.060 after the learning phase, and 0.046 after the intervention.

23–28 October 2001, Melbourne, Australia Conclusions: When well-trained certified examiners perform NT screening, continuous evaluation of the distribution of the NT MoM seems to be a good method to assess the quality for a center and may also be used to identify individual examiners deviating from the mean

FC03: Aneuploidy performance. Intervention towards the examiners seems to decrease variation, which should theoretically decrease the false positive rate. The image-scoring methods we introduced cannot be recommended for quality control in an NT screening program.

FC03a: OBSTETRICS MISCELLANEOUS F22 The importance of funneling to the level of a cervical cerclage J. M. O’Brien, A. L. Hill & J. R. Barton Purpose: Our purpose was to evaluate the utility of ultrasound surveillance after cerclage placement and to propose a rationale for cervical sonography in this setting. Methods: A retrospective case series was evaluated. Women undergoing cervical cerclage by a maternal–fetal medicine specialist regardless of indication and delivering between January 1999 and April 2001 were included. Transvaginal assessment of cervical length and the degree of cervical funneling after cerclage were compared to preoperative values and to outcomes. Funneling to the cerclage was defined as membranes prolapsing down the endocervical canal until they reached the plane of the cerclage. Results: A total of 53 cases were available for analysis. Cervical cerclage resulted in a significant increase in cervical length as the mean length increased from 2.1  1.2 cm to 2.9  0.8 cm after the procedure, P < 0.001, but this measure was not correlated with gestational age at delivery. Funneling to the level of the cerclage, however, was associated with an earlier gestational age at delivery 31.3  5.6 weeks vs. 36.8  2.8 weeks for those cases without this finding, P < 0.001. This observation was statistically significant irrespective of the indication for the procedure and was noted by 28 weeks’ gestation in all patients followed. The incidence of premature rupture of the membranes was also significantly greater postcerclage in women with descent of the membranes to the cerclage (52%) vs. those without this finding (3%, P ¼ 0.002). Conclusions: Funneling to the cerclage has predictive value for earlier preterm delivery in patients who have undergone cervical cerclage. Serial sonography up to 28 weeks’ gestation may be useful in identifying patients at higher risk for premature rupture of the membranes.

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