Nuchal translucency and nasal bone for trisomy 21 screening: single center experience.

AIM: To evaluate the feasibility and diagnostic accuracy of fetal nuchal translucency and nasal bone assessment at 11-14 weeks for screening of trisomy 21 at a single center. METHODS: Nuchal translucency measurement and nasal bone evaluation in relation to the fetal karyotype for singleton fetuses were retrospectively assessed at the Ospedale Microcitemico, Cagliari, Italy, in a three-year period (2001-2004). Nuchal translucency was considered enlarged if greater than or equal to the 95th centile for crown-rump length (CRL) of the reference ranges, and nasal bone was described as present or absent during the evaluation of the fetal facial profile. Sensitivity and specificity for trisomy 21 were assessed for nuchal translucency and absent nasal bone. RESULTS: Among 32,000 cases recorded in the database including fetuses from 11 to 14 weeks, 16,654 fetuses were included in the study with both nuchal translucency measurement and nasal bone evaluation. Median maternal age was 32 years (range, 14-49). In 854 fetuses (5.1%), nuchal translucency was greater than the 95th centile, and 744 (87.1%) of them had a normal karyotype. Among 141 (0.8%) diagnosed cases of chromosomopathies, there were 96 cases of trisomy 21. Nuchal translucency was enlarged in 110 chromosomopathies and in 72 trisomies 21. Sensitivity was 75.0% (95% confidence interval [CI], 65.5-82.6), and specificity 95.5% (95% CI, 95.2-95.8). In fetuses with enlarged nuchal translucency and normal karyotype, there were 30 structural defects (4%), and among these, 15 heart defects (2%). Measurement of nuchal translucency was possible in all cases where it was attempted. In 13 cases (0.1%), it was not possible to determine the visibility of the nasal bone. In 16,486 cases, the nasal bone was defined as visible and in 155 cases (0.9%) the nasal bone was described as absent. The nasal bone was absent in 56 trisomies 21 and in 23 other chromosomopathies, as well as in 76 normal karyotype fetuses. The sensitivity was 58.3% (95% CI, 48.3-67.7) and specificity 99.5% (95% CI, 99.4-99.6). The sensitivity of enlarged nuchal translucency and nasal bone was 80.2% (95% CI, 71.1-86.9). CONCLUSIONS: Enlarged nuchal translucency and absent nasal bone are useful markers of trisomy 21 in the first trimester ultrasound screening, increasing the sensitivity of detection of affected fetuses.

Nuchal translucency measurement at different crown-rump lengths along the 10- to 14-week period for Down syndrome screening.

OBJECTIVES: To evaluate the screening accuracy for Down syndrome of nuchal translucency (NT) measurement at different crown-rump length (CRL) subgroups along the 10- to 14-week period. METHODS: NT was classified 'enlarged' if greater than or equal to 1.5 and 2.0 multiples of the regressed median. Accuracies for Down syndrome (formula=[(TP + TN)/(TP + TN + FP + FN)]x100, where TP: true positive, TN: true negative, FP: false positive, FN: false negative) were evaluated in four classes of CRL: 38-44 mm, 45-54 mm, 55-70 mm, and 71-84 mm, and compared. RESULTS: Of 20 743 fetuses, 20 611 were with no chromosomal abnormalities and 132 were with Down syndrome. Down syndrome fetuses with enlarged NT were 99 (greater than or equal to 1.5 MoM) and 86 (greater than or equal to 2.0 MoM). Sensitivity decreased with gestation, while specificity increased, resulting in increasing likelihood ratios with gestation for each of the CRL groups (8.1, 14.1, 16.3, 17.1 with the use of the 1.5 MoM cut-off, and 13.2, 27.1, 50.1, 84.1 for the 2.0 MoM cut-off). The accuracy increased with gestation (89%, 95%, 95%, 96% with the use of the 1.5 MoM cut-off, and 94%, 97%, 98%, 99% for the 2.0 MoM cut-off, for each of the CRL groups), differences being statistically significant between periods in half of the comparisons. CONCLUSIONS: Although sensitivity of NT assessment for Down syndrome screening decreased as gestation advanced from the 10th to the 14th week, accuracy showed a remarkable increase. These changes should be taken into account in defining and improving the Down syndrome screening policies.

Changes in nuchal translucency thickness in normal and abnormal karyotype fetuses.

OBJECTIVE: To investigate the dynamic trend of the nuchal translucency thickness between fetuses with normal and abnormal karyotype. DESIGN: Prospective observational study. SETTING: Ospedale Microcitemico, Cagliari, Italy. POPULATION: A cohort of 305 first trimester fetuses. METHODS: Fetuses with a nuchal translucency greater than or equal to the 95th centile were invited for a second nuchal translucency measurement. The finding of an 'increased or unchanged' or 'diminished' thickness was compared in fetuses with normal and abnormal karyotype. MAIN OUTCOME MEASURES: Nuchal translucency and karyotype. Median maternal age was 35 years (min 17, max 44) and median crown-rump length at first visit was 50 mm (min 38, max 80). A second nuchal translucency measurement was carried out in 292 fetuses, resulting in increased or unchanged values in 95 cases and decreased nuchal translucency in 197 cases. Two hundred and twenty-six (77.4%) fetuses had normal karyotype and 66 (22.6%) had abnormal karyotype (44 trisomies 21, 10 trisomies 18, 5 trisomies 13, 4 cases of 45 X0, 1 case of 47,XXY, 1 case of 47,XXX and 1 translocation). In the 66 chromosomally abnormal fetuses, the second nuchal translucency measurement was enlarged or unchanged in 37 (56%), and diminished in 29 (44%), while in the 226 normal fetuses the second nuchal translucency measurement was enlarged or unchanged in 58 cases (25%) and diminished in 168 (75%) (relative risk 2.6, 95% confidence interval 1.7-4.0). CONCLUSION: In fetuses with abnormal karyotype, the second nuchal translucency measurement tends to be increased or unchanged, while in normal cases the size of nuchal translucency is generally reduced.

Absence of fetal nasal bone and aneuploidies at first-trimester nuchal translucency screening in unselected pregnancies.

OBJECTIVES: The absence of nasal bone (NB) has been noted in trisomy 21 fetuses at first-trimester ultrasound, in high-risk pregnancies. In this study, the nasal bone was evaluated in relation to fetal karyotype, in unselected pregnancies. METHODS: From September 2001 to September 2002, the fetal facial profile was examined at the 11 to 14 weeks' scan for screening by nuchal translucency (NT). Risks for trisomy 21 were calculated using the Fetal Medicine Foundation's software, and the presence or absence of NB was noted. Prenatal karyotype and pregnancy outcomes were recorded. RESULTS: NT screening was performed in 5532 fetuses from 5425 pregnancies (85 twins, 8 triplets, 2 quadruplets). The visualization of fetal profile was obtained in 5525 fetuses (99.8%), and in 5491 fetuses (99.4%) the NB was present and in 34 cases (0.6%) it was absent. Fetal karyotype and pregnancy outcome were available in 3503 pregnancies, and 40 chromosomal abnormalities were diagnosed (27 trisomies 21, 5 trisomies 18, 2 trisomies 13, 3 Turner syndromes, 1 partial trisomy 9 and 2 others). The NB was absent in 19 (70%) trisomies 21, 4 trisomies 18 (80%), 2 Turner syndromes (66%), in the partial trisomy 9, in 7 normal karyotype fetuses (0.2%), and in a case with spontaneous first-trimester abortion before prenatal diagnosis. A significant difference was found between NT thickness, expressed as a multiple of the median, in trisomy 21 fetuses with present and absent nasal bone. CONCLUSIONS: The absence of NB at 11 to 14 weeks is more frequent in fetuses with trisomy 21 and other aneuploidies than in normal karyotype fetuses.

Neural tube defects in the offspring of thalassemia carriers.

OBJECTIVES: The risk of neural tube defects (NTDs) is negatively correlated with maternal folate levels in early pregnancy. Thalassemia carriers often have reduced red cell folate contents. The aim of this study was to verify whether thalassemia carriers are at increased risk of having offspring with a NTD. METHODS: We retrospectively evaluated the prevalence of thalassemia carriers among 75 women who had prenatal diagnoses of NTDs made at our center. RESULTS: The prevalence of beta-thalassemia carriers among the affected pregnancies was significantly higher than in the general population (22.5 versus 14%, p < 0.05, chi(2) test). CONCLUSION: Although inconclusive, these data indicate that folate supplementation is mandatory among women with thalassemia who are planning a pregnancy.