NT Measurement Research Articles

Frontomaxillary facial angle measurement at 11+0 to 13+6 weeks’ gestation. Application in every day prenatal diagnosis of Trisomy 21

The aim of the study was to evaluate the effectiveness of prenatal screening for trisomy 21 with the use of the FMF angle measurement, depending on the disease risk group. The study included 2,026 single pregnancy fetuses, examined in years 2009-2011. The crown-rump length, nuchal translucency and frontomaxillary facial angle were measured for each of the fetuses according to the Fetal Medicine Foundation guidelines. All ultrasound exams were performed using trans-abdominal probes paired with Voluson 730 Expert and Expert E8 systems. All physicians conducting the exams were FMF-certified professionals. Maternal age at the time of the study was also reported. In 1621 pregnant women serum concentration of PAPP-A was determined using Delfia Express system (Perkin Elmer). Astraia software was used to assess fetal risk of trisomy 21. The final analysis included 791 fetuses which were followed up for the occurrence of trisomy 21. Data were analyzed using PQStat package ver 1.4.2.324. Highly significant likelihood was set at p < 0.01 and significant likelihood at p < 0.05. Average maternal age was 31.42 years (median: 32 in a range from 27 to 45). Average FMF angle was 76.24 degrees (median: 75 degrees in a range from 69 to 04). Average CRL measurements was 63.70 mm (median: 64.10 mm in a range from 45 to 84). Average NT measurement was 1.91 mm (median: 1.6 mm in a range from 0.50 to 9.3). There was no significant (p > 0.05) correlation between maternal age and FMF. Highly significant (p < 0.01) negative correlation between the CRL and the FMF angle was found. There were 41 fetuses with trisomy 21 (Down syndrome) in the study group. In the normal karyotype group, the FMF angle was highly significantly lower (p < 0.0001) than in the trisomy 21 group. 95th percentile of the each of four separated CRL ranges was calculated. Detection rate and false positive rate for each of four different risk levels were estimated. They were used as cutoff points for two models of first trimester screening compared: Model 1, including maternal age, NT measurement and PAPP-A test, and Model 2, including maternal age, NT measurement, PAPP-A test and Frontomaxillary facial angle measurement. 1. Detection rate (DR) of the Down syndrome increases after the introduction of FMF angle measurement as an additional component of screening including maternal age, NT measurement and PAPP-A test. 2. Introduction of the FMF angle as an independent marker for fetal trisomy 21 risk requires further research on large populations.

Comparative studies of two dimensional and three dimensional ultrasonic nuchal translucency in trisomy assessments

Current two-dimensional (2D) ultrasonic marker measurements are inherent with intra- and inter-observer variability limitations. The objective of this paper is to investigate the performance of conventional 2D ultrasonic marker measurements and proposed programmable interactive three-dimensional (3D) marker evaluation. This is essentially important to analyze that the measurement on 3D volumetric measurement possesses higher impact and reproducibility vis-à-vis 2D measurement. Twenty three cases of prenatal ultrasound examination were obtained from collaborating hospital after Ethical Committee's approval. The measured 2D ultrasonic marker is Nuchal Translucency or commonly abbreviated as NT. Descriptive analysis of both 2D and 3D ultrasound measurement were calculated. Three trial measurements were taken for each method. Both data were tested with One-Sample Kolmogorov-Smirnov Test and results indicate that markers measurements were distributed normally with significant parametric values at 0.621 and 0.596 respectively. Computed mean and standard deviation for both measurement methods are 1.4495 ± 0.46490 (2D) and 1.3561 ± 0.50994 (3D). ANOVA test shows that computerized 3D measurements were found to be insignificantly different from the mean of conventional 2D at the significance level of 0.05. With Pearson's correlation coefficient value or R = 0.861, the result proves strong positive linear correlation between 2D and 3D ultrasonic measurements. Reproducibility and accuracy of 3D ultrasound in NT measurement was significantly increased compared with 2D B-mode ultrasound prenatal assessment. 3D reconstructed imaging has higher clinical values compare to 2D ultrasound images with less diagnostics information.

First trimester versus second trimester down's syndrome screening in the west of Scotland

During 2010, we compared performance of first versus second trimester Down's syndrome screening in 2 hospitals 4 miles apart, serving the same population in West of Scotland. As the same...

Effect of image settings on nuchal translucency thickness measurement by a semi‐automated system

To investigate whether pre- and post-processing image settings affect NT measurements made by a semi-automatic method (SAM). Different image settings (e.g. gain) were either adjusted one at a time on images that had been obtained during fetal NT scans (post-processing, n = 66), or adjusted one at a time during live scanning and image acquisition of the adult posterior tibial artery (pre-processing group, n = 91). The NT and luminal diameter of the posterior tibial artery, respectively, were measured by SAM on all original and adjusted images. Alteration of the image settings resulted in a statistically significant effect on the measurements taken by SAM, with an average pair difference ranging from 0.001 mm to 0.139 mm. Most of the differences were small and therefore the clinical impact would be negligible. The pair differences were greatest with a very high contrast setting, or without tissue harmonic imaging (THI); the paired difference in measurement in those with vs those without THI was more than 0.1 mm in over 40% of cases. Measurements made by SAM are affected by image settings.

Screening auf Trisomie 18 und Trisomie 13 durch das kombinierte Anwenden der Risiko-Algorithmen für Trisomie 21, 18 und 13

Assessment of first-trimester combined screening for trisomy 18 and 13 with the combined use of the risk algorithms for trisomy 21, 18 and 13. First-trimester combined screening based on maternal and gestational age, fetal NT, PAPP-A and free β-hCG was assessed in 39 ,004 pregnancies. Patient-specific risks for trisomy 21, 18, 13 were computed based on the current FMF London algorithm. The study population consisted of 38 ,751 singleton pregnancies including 39 cases with trisomy 18 or 13. In the aneuploid group, median delta NT was 0.72 mm, PAPP-A was 0.21 MoM and free β-hCG was 0.33 MoM. Although only 41 % of the NT measurements of fetuses with trisomy 18 or 13 were above the 95th percentile, the detection rates for trisomy 18 or 13 were 82 % with the trisomy 18/13 algorithm and 56.4 % with the trisomy 21 algorithm. The respective false-positive rates were 0.7 % and 4.7 %. The combination of the trisomy 18/13 and the trisomy 21 algorithm with the same cut-offs led to a detection rate of 94.9 % at an overall false-positive rate of 5.0 %. Despite a substantial underestimation of the fetal NT, the combined use of the trisomy 18/13 and the trisomy 21 algorithm of the FMF London leads to a detection rate for trisomy 18/13 of about 95 % for a false-positive rate of 5.0 %.

Prospective detection of open spina bifida at 11–13 weeks by assessing intracranial translucency and posterior brain

We describe a case series of six fetuses with open spina bifida (OSB) from four different prenatal units, where the anomaly was detected at the routine 11-13-week ultrasound examination. Crown-rump length ranged from 49 to 78 mm. All cases were first suspected during nuchal translucency thickness measurement in the mid-sagittal plane of the face. OSB was lumbosacral in five fetuses and cervical in one. The intracranial translucency (IT) was obliterated in two cases, but some fluid was found in the other four cases. However, in all cases the typical landmarks of a normal posterior brain and normal IT were absent. In all six cases the ratio of brainstem diameter to brainstem-occipital bone distance was increased (≥ 1). This detection of an abnormal posterior brain led to a targeted examination and detection of the spinal lesion during the same examination in five cases, whereas in one suspicious case the patient was recalled at 17 weeks, when the abnormality was detected. Two fetuses had both multiple anomalies and trisomy 18. These prospective cases demonstrate the feasibility of using the standard mid-sagittal plane commonly used for NT measurement to assess the IT and the posterior brain and to determine the presence of OSB during NT screening.

Quality assurance of nuchal translucency for prenatal fetal Down syndrome screening

Objective: To assess the quality of nuchal translucency, (NT) measurements were performed at four public institutions performing routine first trimester combined prenatal screening for Down syndrome. Methods: The median of the NT-MoM distribution and standard deviation (SD) of the log10 NT-MoM were determined. Sonographers and screening centres distributions were assessed for measures of central tendency (median) and dispersion (log10 SD). Cumulative Sum (CUSUM) charts were created to assess whether screening centres and individual sonographers who had performed at least 30 NT measurements exhibited any systematic bias by checking whether their CUSUM scores exceeded predefined upper and lower control limits. Results: Of the 36 sonographers, only 67% (n = 24) had performed 30 or more scans. The median NT-MOM at each screening centre ranged from 1.02 to 1.09. Screening centre standard deviations ranged from 0.073 to 0.099. CUSUM charts indicated that only one screening centre remained within the predefined control limits throughout the assessment period. Analysis of variance indicated that a statistically significant difference existed between the log NT-MoM distributions of the individual sonographers (F = 10.7; p <0.0001). Inspection of the individual sonographer CUSUM charts indicated that 11 (45%) of the 24, with more than 30 NT measurements were either under or over measuring the NT. Conclusion: Prospective monitoring and feedback of quality assurance assessment results of sonographers and screening centres should be routinely reported as both are responsible, if equity of screening performance is to be maintained.

OP11.04: Continuing education on NT: an exercise on caliper placement for NT measurement

Objectives: During the first trimester screening, NT measurement is one of the main components in calculating the risk for trisomies. Systematic error is common among accredited sonographers in audit trail. According to the Fetal Medicine Foundation criteria for NT measurement, the calipers should be placed at the thickest area of the subcutaneous translucency with the calipers’ arm flush with the line. The objective of this study is to observe the effectiveness of an alignment exercise in improving the accuracy of individual sonographers in caliper placement. Methods: Twenty mid sagittal pictures suitable for NT measurement were selected. Each picture is duplicated into a set of 4 pictures with different caliper placements. (A total of 20 sets= 80 pictures). Fifteen FMF accredited sonographers from two of the teaching hospitals in Singapore took part in the exercise. Twenty MCQ questions were created with these 20 sets of pictures. One out of each set of 4 pictures has the ideal caliper placement. The results were assessed anonymously using an electronic voting system. The aggregate scores were disclosed after each question. The same procedure was repeated again after a 20 minute short revision lecture on criteria of NT measurement by a FMF accredited trainer. The results were saved and statistically analysed for the individual and group accuracy of measurement before and after the lecture. Results: The results are shown in Table 1. Conclusions: There is a statistically significant improvement in caliper placement for FMF accredited sonographers after a caliper placement exercise and lecture. The improvement happened for the sonographers in both the hospital. Continuing education and refresher courses for caliper placement should be conducted from time to time to standardize the caliper placement for FMF accredited sonographers.

P06.08: A comparison of first trimester 3D multiplanar sonography in the obese and non‐obese population

Conclusions: The new NT mixture model challenges our classical approach of quality control. LHR-based quality control process is feasible at 11–14 weeks. The approach offers a sensitive approach to the quality of NT measurement and takes into account the mixture model of distribution. It could also be applied to biochemical markers as well as to the entire combined process of first trimester screening.

P08.01: The role of color Doppler in the diagnosis of fetal malformations

Ultrasound measurement of nuchal translucency thickness is nowadays a widely used tools to evaluate the risk of fetal chromosomal abnormality in a combined screening with maternal biochemistry evaluation. Up to 75% of aneuploid fetuses have increased NT, but increased NT is also found in about 5% of normal karyotyping fetuses. In normal karyotypes, high NT thickness can be associated with different abnormalities such as congenital heart disease, skeletal dysplasias, metabolic and neuromuscular disorders or simply to a physiological fetal development. We present a case of increased nuchal translucency with normal karyotyping fetus and developmental disorder. A 28-year-old gravida 1 para 0 woman presented at 10 weeks 4 days (crown–rump length = 40.4 mm) for a first-trimester ultrasound evaluation. An increased NT measurement of 4.0 mm was noted (>99th centile) and 1 weeks later, still remained. Result of the amniocentesis was that of a normal 46, XO. A fetal echocardiogram performed at 20 weeks was within normal limits. The remainder of the pregnancy was uneventful and the patient delivered a full-term female infant weighing 3.52 kilogram, Apgar score was (9/10). At 40 days of age, the child visited hospital for asymmetric cervical positioning. Cervical spine x-ray and neck sonogram was normal. 4 month later, developmental delay was noted and the child started rehabilitation training for torticolis. Increased NT in first trimester with normal karyotype fetus, motor development delayed with the unrecognizable syndrome should be considered.

P06.07: Effect of maternal age on patient choice for first trimester screening for chromosomal abnormalities on a private Fetal Medicine Unit in Brazil

Conclusions: The new NT mixture model challenges our classical approach of quality control. LHR-based quality control process is feasible at 11–14 weeks. The approach offers a sensitive approach to the quality of NT measurement and takes into account the mixture model of distribution. It could also be applied to biochemical markers as well as to the entire combined process of first trimester screening.

Ductus venosus pulsatility index measurement reduces the false‐positive rate in first‐trimester screening

To investigate if ductus venosus (DV) pulsatility index for veins (PIV) and a-wave measurements can increase the accuracy of first-trimester Down syndrome screening in a high-risk population. The database of our fetal medicine unit was searched for all cases at increased first-trimester Down syndrome risk. Multivariable logistic regression was used to construct a prediction rule for chromosomal anomalies at any given maternal age, nuchal translucency multiples of the median (NT-MoM) and DV-PIV MoM. The discriminative ability of the model was assessed by using receiver-operating characteristics (ROC) analysis. The study population included 445 fetuses. DV-PIV was increased (≥ 95(th) percentile) in 239 (54%) and DV a-wave was abnormal in 187 fetuses (42%). In this cohort, 80% of all chromosomal anomalies were identified by an increased DV-PIV and 68% by an abnormal a-wave. The odds of chromosomal anomalies increased by a factor of 4.2 per MoM increase in DV-PIV, adjusted for NT and maternal age. The area under the ROC curve for the prediction of chromosomal anomalies was 0.79. After correction for DV-PIV, DV a-wave did not significantly add to the prediction of chromosomal anomalies. In a population of fetuses at increased first-trimester risk for Down syndrome, the combination in a logistic regression model of NT, DV-PIV and maternal age can improve the accuracy of screening for trisomy 21 and other chromosomal anomalies. This is the first study that models the additional value of DV-PIV as a continuous variable to NT measurement alone in a high-risk first-trimester population.

OP17.01: Likelihood ratio based quality control for NT measurement at first trimester

OP17.01: Likelihood ratio based quality control for NT measurement at first trimester

OP34.11: Knowledge of first trimester NT measurement at birth is used to predict LGA and macrosomia at term

OP34.11: Knowledge of first trimester NT measurement at birth is used to predict LGA and macrosomia at term

P22.01: Efficacy and length of routine transabdominal fetal heart scanning at the time of NT measurement

P22.01: Efficacy and length of routine transabdominal fetal heart scanning at the time of NT measurement

725: Abnormal nuchal translucency: the benefits of biochemistry

When NT is abnormal, the adjusted aneuploidy risk is often high regardless of biochemistry (BC). Our objectives were to evaluate the influence of age and degree of NT abnormality on ranges of adjusted risk, and to assess the potential of BC to distinguish those at high-risk of Down syndrome (T21) vs. Trisomy 18 or 13. Singleton pregnancies undergoing risk assessment at 11-14 weeks from 2003-2008 were reviewed, and those with NT measurements ≥3.0mm were identified. Adjusted risks for T21 and T18/13 were based on age, NT, and BC (PAPP-A and free β-hCG). Ranges of adjusted T21 risk were calculated for different age and NT groups. 18,951 pregnancies underwent risk assessment, and 190 pregnancies (1.0%) had NT ≥3.0mm. There were 67 chromosomal abnormalities, including 34 T21, 16 T18, and 5 T13. The range of adjusted T21 risks based on age and NT measurement are seen in the Table. The rate of adjusted risk <1 in 100 for NTs of 3.0-3.5mm, 3.6-4.0mm, 4.1-5.0mm, and >5.0mm were 44%, 11%, 4%, and 3%, respectively. BC was very useful in identifying cases at high risk of T21 vs. T18/13: In cases of T21, median adjusted risk of T18/T13 was 1 in 289. In cases of T18 and T13, the median adjusted risk of T18/T13 was 1 in <5.Tabled 1Range of Down Syndrome Risk based on Age and NTNT 3.0-3.5mm (n=92)NT 3.6-4.0mm (n=38)NT 4.1-5.0mm (n=26)NT <5mm (n=34)Age <301:42舁-舁10681:14舁-舁1891:舁<5舁-舁1511 in 139Age 31-351: <5 - 7951: <5 - 1521: <5 - 471: <5 - 55Age 36-401: <5 - 3291: <5 - 551: <5 - 171: <5 - 27Age >401: <5 - 231: <5 - 131: <51: <5 Open table in a new tab The ranges of adjusted T21 risk in younger women and those with less extreme NT values were broad. Defining a NT cutoff above which BC is not performed may not be useful, particularly when specific age or risk cutoffs are not used to identify candidates for invasive testing. In addition, BC may be helpful in those patients who would be interested in prenatal diagnosis of T18 or 13, but not T21.

Long-term Outcome of Pregnancies with Increased Nuchal Translucency and Normal Karyotype

Abstract Objectives The aim of this study was to examine the prevalence of major and minor anomalies according to the increase of NT thickness. Methods This is a long-term retrospective study in which singleton gestations of euploid fetuses with increased NT were analyzed. NT measurement was performed in the first trimester examination according to the criteria of fetal medicine foundation (FMF) when the fetal crown-rump length (CRL) was 45 to 84 mm. The cases were followed up from 1 to 5 years postpartum to assess the presence of CHD and to point out other anomalies that could be associated with increased NT. Results The outcome of 133 cases could be analysed out of 198 pregnancies of which in 55 cases some congenital anomalies (minor or major) were revealed up to the 5 years of life (prevalence of 41.4%). The prevalence of CHDs, including the defects of the great vessels, stood out among the others. In the group with NT between 95th and 99th centiles four cases with minor heart problems were identified (11.1%, 4/36). The rate of major cardiac defects proved to be 13.3% (6/45) in the group with NT between 3.5-4.4 mm, and 17.3% (9/52) in the group with NT &gt; 4.5 mm. Among the 35 healthy children with various minor health problems not related to the presence of increased nuchal translucency there were 7 cases with hydrocele. In 3 of them it was associated with unilateral inguinal hernia but in 3 it was isolated and one was part of a complex malformation (The rate of other organ-specific anomalies did not prove to be significant). In the whole study population only thirteen cases (9.8%) ended up in intrauterine death, or arteficial abortion. Conclusion The prevalence of major cardiac defects as well as other major anomalies increases with fetal nuchal thickness. Since the prevalence of CHD is 100 times higher in the population of fetuses with NT above 4.5 mm, specialist fetal echocardiography should be offered in the second trimester together with other follow-up investigations. Among the children without any major abnormalities, a high number of minor anomalies were revealed during the long-term follow-up. These anomalies do not have significant disadvantage to the quality of life, but some of them necessitates short or long-term medical treatment and this should also be leveled with the future parents. Despite the numerous investigations the exact etiology of increased NT remains unknown. The relatively high prevalence of hydrocele in the newborns in our material raises the question wheather it is related to the presence of NT in the fetal period because of abnormal lymphatic development or alterations in the extracellular matrix. Further long-term follow-up studies could probably contribute to find explanation on the etiology of increased NT in the first trimester. These data can be used when counseling parents of euploid fetuses with increased fetal NT.

P16.04: Significance of 2.5-3.5 mm NT measurements

P16.04: Significance of 2.5-3.5 mm NT measurements

P11.19: Gender of fetuses with 2.5-3.5 mm NT measurements

P11.19: Gender of fetuses with 2.5-3.5 mm NT measurements

OP02.04: A NTMoM and DVPIVMoM based model to predict outcome in fetuses at increased first trimester risk: a promising method to reduce false positive rates

from the vertical position of the occipitofrontal diameter axis. The operators were blinded to their measurements; the 60 3D blocks were analysed twice by each operator. Mean difference and 95% limits of agreement between paired measurements of fetal NT by the same and by two different sonographers were determined. Results: In the mid-sagittal plane the median NT was 1.8. The median NT at 5◦ to 25◦ was significantly lower (−0.1, −0.3, −0.4, −0.5, −0.6 mm) than in the mid-sagittal plane. The 95% limits of agreement for NT in the mid-sagittal section were −0.1 to 0.3 mm and −0.1 to 0.5 mm for both operators. At 15◦ for delta NT, 95% of the cases were between −0.2 to 0.7 mm and −0.3 to 0.5 mm, respectively. Between operators it was −0.1 to 0.2 in the mid-sagittal section and −0.1 to 0.4 at a deviation of 15◦. Conclusion: Fetal NT measurement depends on the position of the fetal head. The measurement is biggest in the mid-sagittal plane, which is clearly defined and smaller in lateral planes.