United States' experience in nuchal translucency measurement: variation according to provider characteristics in over five million ultrasound examinations.

OBJECTIVE: The Nuchal Translucency Quality Review (NTQR) program has provided standardized education, credentialing and epidemiological monitoring of nuchal translucency (NT) measurements since 2005. Our aim was to review the effect on NT measurement of provider characteristics since the program's inception. METHODS: We evaluated the distribution of NT measurements performed between January 2005 and December 2019, for each of the three primary performance indicators of NT measurement (NT median multiples of the median (MoM), SD of log10 NT MoM and slope of NT with respect to crown-rump length (CRL)) for all providers within the NTQR program with more than 30 paired NT/CRL results. Provider characteristics explored as potential sources of variability included: number of NT ultrasound examinations performed annually (annual scan volume of the provider), duration of participation in the NTQR program, initial credentialing by an alternative pathway, provider type (physician vs sonographer) and number of NT-credentialed providers within the practice (size of practice). Each of these provider characteristics was evaluated for its effect on NT median MoM and geometric mean of the NT median MoM weighted for the number of ultrasound scans, and multiple regression was performed across all variables to control for potential confounders. RESULTS: Of 5 216 663 NT measurements from 9340 providers at 3319 sites, the majority (75%) of providers had an NT median MoM within the acceptable range of 0.9-1.1 and 85.5% had NT median MoM not statistically significantly outside this range. Provider characteristics associated with measurement within the expected range of performance included higher volume of NT scans performed annually, practice at a site with larger numbers of other NT-credentialed providers, longer duration of participation in the NTQR program and alternative initial credentialing pathway. CONCLUSIONS: Annual scan volume, duration of participation in the NTQR program, alternative initial credentialing pathway and number of other NT-credentialed providers within the practice are all associated with outcome metrics indicating quality of performance. It is critical that providers participate in ongoing quality assessment of NT measurement to maintain consistency and precision. Ongoing assessment programs with continuous feedback and education are necessary to maintain quality care. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Real-time quality control of nuchal translucency measurements using the exponentially weighted moving average chart.

OBJECTIVE: The establishment of ongoing audits for first-trimester nuchal translucency (NT) measurements is of paramount importance. The exponentially weighted moving average (EWMA) chart has been published as an efficient tool for NT quality control with the advantages of being suitable for real-time long-term monitoring. This study aimed to assess the efficacy of real-time NT quality control using EWMA charts. MATERIALS AND METHODS: This was an ongoing prospective study conducted from January 2011 to December 2017 at the Centre for Fetal Medicine Gennet in Prague. The quality of NT measurements was assessed using the NT retrospective distribution parameters and EWMA charts, and the results were presented to the sonographers during collective meetings. RESULTS: Overall, 28,928 NT measurements obtained from six sonographers were eligible for the study. Looking at individual EWMA charts, we observed four main outcomes. First, there was a clear improvement in the performance of sonographers with initially poor performances. Second, the performance of sonographers with an initially satisfactory quality was maintained. Third, there was an observed deterioration of the performance without the audits. Last, the sonographers appreciated an unequivocal and straightforward graphical presentation of EWMA curves. CONCLUSION: EWMA proved to be an efficient and suitable tool for real-time monitoring of NT quality and led to an overall improvement of the sonographers' performance.

The indications for early prenatal diagnosis of trisomy 18: a 7-year experience at mainland China.

Objective: To report the experience with first-trimester prenatal detection of pregnancies complicated by trisomy 18.Study design: Proven cases of trisomy 18 identified between 11 and 14 weeks of gestation were retrospectively reviewed. Information on maternal demographics, prenatal sonographic findings, indications for prenatal diagnosis and chromosomal analysis results was obtained by reviewing medical records.Results: During the 7-year period from January 2011 to December 2017, 89 cases of full trisomy 18 had first-trimester indications for prenatal diagnosis at Guangzhou Women and Children's Medical Center. Eighty-five (95.5%) had abnormal sonographic findings in the first trimester. The most common finding was increased nuchal translucency (55.1%), followed by cystic hygroma (18.0%), omphalocele (14.6%), and fetalis hydrops (11.2%). Four cases (4.5%) were not associated with any abnormal first-trimester sonographic finding, and were diagnosed because of routine positive screening results for trisomy 18. A single case was diagnosed because of a positive cell-free DNA (cfDNA) result.Conclusion: These results demonstrate that a large number of fetuses with trisomy 18 have abnormal sonographic findings in the first trimester, and support the continued utility of first-trimester sonographic examination in the diagnosis of this trisomy even with the availability of cfDNA.

Sonologist's characteristics related to a higher quality in fetal nuchal translucency measured in primary antenatal care centers.

OBJECTIVE: To assess the quality of nuchal translucency (NT) measurements in primary care and the sonologist's characteristics related with a higher quality. METHODS: The median NT expressed in multiples of the median (MoM) was calculated for each sonologist of 14 participating antenatal primary care centers of the Catalan Institute of Health. A survey to the sonologists was used to establish variables related to higher-quality measurements. RESULTS: The median NT MoM obtained in 16 448 NT measurements, performed by 102 sonologists, was 0.94 MoM. NT underestimation was observed in 46% of the sonologists. Underestimation were less frequent among professionals who performed more than 230 ultrasounds per year (26% vs 53%;p = .022), those who completed the online Fetal Medicine Foundation (FMF) course (22% vs 54%; p = .021), and those who were subject to periodic audits (24% vs 56%; p = .021). Underestimation rate decreased from 60%, to 33% and 14% with the increase of the years of experience from less than 5 years, to 6 to 15 years and more than 15 years of experience, respectively (p = .029). CONCLUSIONS: Higher-quality measurements were demonstrated in sonologists who performed more ultrasounds per year, those with more years of scanning experience, those who completed the online FMF course, and those periodically audited.

Clinical application of chromosomal microarray analysis in fetuses with increased nuchal translucency and normal karyotype.

BACKGROUND: Submicroscopic chromosomal imbalance is associated with an increased nuchal translucency (NT). Most previous research has recommended the use of chromosomal microarray analysis (CMA) for prenatal diagnosis if the NT ≥ 3.5 mm. However, there is no current global consensus on the cutoff value for CMA. In this study, we aimed to discuss the fetuses with smaller increased NT which was between cutoff value of NT for karyotype analysis (NT of 2.5 mm in China) and the recommended cutoff value for CMA (NT of 3.5 mm) whether should be excluded from CMA test. METHODS: Singleton pregnant women (N = 192) who had undergone invasive procedures owing to an increased NT (NT ≥ 2.5 mm) were enrolled. Fetal cells were collected and subjected to single nucleotide polymorphism array and karyotype analyses simultaneously. Cases were excluded if the karyotype analysis indicated aneuploidy and apparent structural aberrations. RESULTS: Fourteen cases of aneuploidy and four cases of structural abnormalities were excluded. Of the remaining 174 cases, 119 fetuses had NTs of 2.5-3.4 mm, and 55 fetuses with NT ≥ 3.5 mm. Eleven copy number variants (CNVs) were identified. In fetuses with smaller NTs, six (6/119, 5.9%) variations were detected, including two (2/119, 1.6%) clinically significant CNVs (pathogenic or likely pathogenic CNV), one  likely benign CNV, two variants unknown significance, and one incidental CNV. Five (5/55, 9.1%) variations were found in fetuses with NT ≥ 3.5 mm. Among these CNVs, three (3/55, 5.5%) cases had clinically significant CNVs, and two had likely benign CNV. There were no statistically significant differences in the incidence of all CNVs and clinically significant CNVs in the two groups (p > 0.05). CONCLUSION: CMA improved the diagnostic yield of chromosomal aberrations for fetuses with NTs of 2.5-3.4 mm and apparently normal karyotype, regardless of whether other ultrasonic abnormalities were observed.

Quality management of nuchal translucency ultrasound measurement in Australia.

BACKGROUND: Nuchal translucency measurement has an established role in first trimester screening. Accurate measurement requires that technical guidelines are followed. Performance can be monitored by auditing the distribution of measurements obtained in a series of cases. AIMS: The primary aim is to develop an accessible, theory-based educational program for individuals whose distribution of measurements at audit falls outside an acceptable range, and assess operator performance following this intervention. MATERIALS AND METHODS: Operators whose nuchal translucency measurement distributions fall outside a normal range (38-65% above the median) were expected to undergo a teleconference tutorial. Accessible from anywhere in Australia, the one hour tutorials were run by a senior sonographer (to explain technical ultrasound aspects) and the audit program manager (to explain the audit process). RESULTS: In 2011, 83 operators attended the teleconference tutorials. Compared to a random comparison group of operators meeting standard in 2011, teleconference tutorial attendees were significantly more likely to: (i) operate in rural or regional, rather than metropolitan, centres (P = 0.001); (ii) be less experienced (P < 0.0005); and (iii) have lower annual scan numbers (P = 0.0012). Improvement in nuchal translucency measurement quality was seen after one audit cycle and was maintained over subsequent years. The mean percentage of the study cohort reaching standard over the five-year audit was 77.8% which was not statistically different from the average for the comparison cohort of all other audited operators (79.3%; P = 0.61). CONCLUSIONS: Teleconference tutorials are a convenient, accessible and effective way to obtain immediate and sustained improvement in operator performance.

The nomogram of prenasal thickness and nasal bone ratio and its relationship with nuchal fold in second-trimester fetal ultrasound.

AIM: We aimed to define the normal values of second-trimester fetal prenasal thickness and nasal bone length ratio (PNT/NBL) in a low-risk Turkish population and investigate the relationship between the increased PNT and nuchal fold (NF). METHOD: We retrospectively reviewed the data of 650 cases considered to be euploid fetuses who presented to our clinic between December 2013 and September 2014 for a second-line ultrasound between 17 and 24 weeks. Their PNT, NBL, NF and biometric (BPD, HC, AC, FL and HL) measurements were recorded. RESULTS: A total of 650 cases considered to be euploid fetuses were included in this study. There was a linear increase in PNT with the gestational weeks (mean value 3.01 at weeks 17-18 and 3.76 at weeks 23-24). The PNT/NB ratio showed a slight decrease in advancing gestational weeks (mean value 0.57 at weeks 17-18 and 0.50 at weeks 23-24). The 95th percentile value of the PNT/NB ratio, independent of the gestational week, was 0.76. The values of both PNT and NF increased with advancing gestational weeks, but there was no statistically linear increase between PNT and NF (R2 : 0.115). CONCLUSION: In this study, we provided a nomogram of the PNT/NB ratio. Both NF thickness and PNT should be dealt with as two separate markers. Although the formation mechanisms are thought to be the same in both of them, a strong linear relationship does not exist between them.

Cut-off value of nuchal translucency as indication for chromosomal microarray analysis.

OBJECTIVES: An association between isolated, increased nuchal translucency thickness (NT) and pathogenic findings on chromosomal microarray analysis (CMA) has been reported. A recent meta-analysis reported that most studies use a NT cut-off value of 3.5 mm. However, considering NT distribution and the commonly accepted 5% false-positive rate in maternal serum screening, NT cut-off levels should be reconsidered. The aim of this study was to assess different NT cut-off levels as indication for CMA and to determine whether CMA should be recommended for mildly increased NT of 3.0-3.4 mm. METHODS: This was a retrospective, multicenter study of singleton pregnancies with CMA results and either normal NT and no other finding or with increased NT as the only medical indication for CMA at the time of an invasive procedure (increased NT was considered an isolated finding in cases of advanced maternal age). Women with normal fetal NT who underwent CMA did so at their own request. A single laboratory performed all genetic analyses. Comparative genomic hybridization microarray analysis or single nucleotide polymorphism array technology was used for CMA. If combined first-trimester screening (NT and biochemistry) indicated increased risk for common aneuploidies, the case was excluded. NT was used to divide cases into three groups (≤ 2.9 mm, 3.0-3.4 mm and ≥ 3.5 mm) and their CMA results were compared. RESULTS: CMA results were recorded in 1588 pregnancies, among which 770 fetuses had either normal NT with no other finding or isolated increased NT. Of these, 462 had NT ≤ 2.9 mm, 170 had NT of 3.0-3.4 mm and 138 had NT ≥ 3.5 mm. Pathogenic copy number variants were found in 1.7%, 6.5% and 13.8% of cases, respectively. CONCLUSION: Our results suggest that CMA should be recommended when fetuses have isolated, mildly increased NT (3.0-3.4 mm). Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

First-trimester reference centiles of fetal biometry in Indian population.

AIM AND OBJECTIVE: To create crown-rump length (CRL)-based biometric chart for fetus in the first trimester among the Indian population. MATERIAL AND METHODS: Cross-sectional data were obtained from 400 singleton pregnancies between 11 and 14 weeks gestation with a normal outcome. Linear regression models were constructed; the mean and SD were derived as a function of CRL. RESULTS: There was a positive correlation of CRL with nuchal translucency (NT) (y = 0.0102x + 0.6307 R2 = 0.1177), biparietal diameter (BPD) (BPD = 0.032*CRL +0.185 R2 = 0.765), occipito-frontal diameter (OFD), lateral ventricular diameter (LV), abdominal circumference (AC) (AC = 0.944*CRL +9.684 R2 = 0.668), femur length (FL) (FL = 0.222*CRL -4.734 R2 = 0.661), fetal weight (FW) (FW = 1.328*CRL -10.41 R2 = 0.662). The regression models and centile charts of NT, BPD, OFD, LV, AC, and FW were constructed. Taking FW as the independent variable, a linear equation of BPD, AC, and FL to calculate weight was constructed. CONCLUSIONS: The first-trimester centile charts of fetal parameters can be used as a reference for Indian population in the determination of gestational age or other adverse outcomes.

Quality Requirements for the early Fetal Ultrasound Assessment at 11-13+6 Weeks of Gestation (DEGUM Levels II and III).

The early fetal ultrasound assessment at 11 - 13(+6) weeks of gestation remains the cornerstone of care despite the progress in diagnosing fetal chromosomal defects using cell-free fetal DNA (cffDNA) from the maternal circulation. The measurement of nuchal translucency (NT) allows the risk calculation for the fetal trisomies 21, 18 and 13 but also gives information on those fetal chromosomal defects which are at present unable to be detected using cffDNA. Nuchal translucency is the only auditable parameter at 11 - 13(+6) weeks and gives thus information on the quality of the first trimester anomaly scan. In addition it gives indirect information on the risks for fetal defects and for cardiac anomalies. Also the chances for a healthy live baby can be estimated. As experience with first trimester anomaly scanning increases, and the resolution of the ultrasound equipment has increased substantially, more and more details of the fetal anatomy become accessible at the first trimester scan. Therefore fetal anatomical defects and complex anomalies have become amenable to examination in the first trimester. This guideline describes compulsory and optional parameters for investigation at the first trimester scan and outlines a structured method of examining a first trimester fetus at 11 - 13(+6) weeks of gestation.

Impact of Including or Removing Nuchal Translucency Measurement on the Detection and False-Positive Rates of First-Trimester Down Syndrome Screening.

INTRODUCTION: First-trimester Down syndrome (DS) screening combining maternal age, serum markers (pregnancy-associated plasma protein-A and beta-human chorionic gonadotropin) and nuchal translucency (NT) gives an 85% detection rate for a 5% false-positive rate. These results largely depend on quality assessment of biochemical markers and of NT. In routine practice, despite an ultrasound quality control organization, NT images can be considered inadequate. The aim of the study was to evaluate the consequences for risk calculation when NT measurement is not taken into account. MATERIAL AND METHOD: Comparison of detection and false-positive rates of first-trimester DS screening (PerkinElmer, Turku, Finland), with and without NT, based on a retrospective study of 117,126 patients including 274 trisomy 21-affected fetuses. NT was measured by more than 3,000 certified sonographers. RESULTS: There was no significant difference in detection rates between the two strategies including or excluding NT measurement (86.7 vs. 81.8%). However, there was a significant difference in the false-positive rates (2.23 vs. 9.97%, p < 0.001). DISCUSSION: Sonographers should be aware that removing NT from combined first-trimester screening would result in a 5-fold increase in false-positive rate to maintain the expected detection rates. This should be an incentive for maintaining quality in NT measurement.

Setting up a Nuchal Translucency Clinic: What Radiologists Need to Know.

The purpose of this article was to discuss the process of setting up a nuchal translucency (NT) screening clinic in clinical practice, how to interpret the information in combination with other clinical tests, what to do if abnormal results are obtained, and to illustrate some of the fetal anomalies that are associated with an increased NT. The NT was initially implemented to predict the likelihood of a fetus with Down syndrome. Maternal age can be combined with fetal NT and maternal serum biochemistry (free ß-hCG and PAPP-A) at 11 to 14 weeks to identify about 90% of affected fetuses. Setting up a clinic to perform the NT screening requires certified physicians and certified sonographers. Certification can be obtained for both physicians and sonographers through Nuchal Translucency Quality Review and Fetal Medicine Foundation. Cell-free DNA testing is now altering what our patients are choosing to evaluate fetuses at risk for chromosomal anomalies and congenital anomalies. Common pitfalls to performing, interpreting, and conveying results of the NT are illustrated in this article. Nasal bone measurement, fetal anatomy examination and fetal echocardiography are tools that add sensitivity to the detection of chromosomal abnormalities. Examples of fetal anomalies discovered during the NT screening are also illustrated. Screening for obstetric complications is an additional benefit to the NT clinic.

Nuchal Translucency Quality Review (NTQR) program: first one and half million results.

OBJECTIVE: To evaluate the performance of first-trimester nuchal translucency (NT) measurement by providers (physician-sonologists and sonographers) within the Nuchal Translucency Quality Review (NTQR) program. METHODS: After training and credentialing providers, the NTQR monitored performance of NT measurement by the extent to which an individual's median multiple of the normal median (MoM) for crown-rump length (CRL) was within the range 0.9-1.1 MoM of a published normal median curve. The SD of log10 MoM and regression slope of NT on CRL were also evaluated. We report the distribution between providers of these performance indicators and evaluate potential sources of variation. RESULTS: Among the first 1.5 million scans in the NTQR program, performed between 2005 and 2011, there were 1 485 944 with CRL in the range 41-84 mm, from 4710 providers at 2150 ultrasound units. Among the 3463 providers with at least 30 scans in total, the median of the providers' median NT-MoMs was 0.913. Only 1901 (55%) had a median NT-MoM within the expected range; there were 89 above 1.1 MoM, 1046 at 0.8-0.9 MoM, 344 at 0.7-0.8 MoM and 83 below 0.7 MoM. There was a small increase in the median NT-MoM according to providers' length of time in the NTQR program and number of scans entered annually. On average, physician-sonologists had a higher median NT-MoM than did sonographers, as did those already credentialed before joining the program. The median provider SD was 0.093 and the median slope was 13.5%. SD correlated negatively with the median NT-MoM (r = -0.34) and positively with the slope (r = 0.22). CONCLUSION: Even with extensive training, credentialing and monitoring, there remains considerable variability between NT providers. There was a general tendency towards under-measurement of NT compared with expected values, although more experienced providers had performance closer to that expected.

Fetal nuchal fold thickness measurement between 18 and 24 weeks of pregnancy: reference intervals for a Brazilian population.

OBJECTIVE: To determine reference intervals of fetal nuchal fold (NF) thickness measurement in the second trimester of pregnancy in a Brazilian population. METHODS: This was a retrospective cross-sectional study with 2559 normal singleton pregnancies between 18 and 24 weeks of pregnancy. The fetal NF was obtained in the axial plane of fetal head at level of lateral ventricles including the cavum septum pellucidum, third ventricle, thalamus and transverse cerebellar diameter. The NF was measured posterior to the occipital bone, from the bone surface to the skin, including only soft tissue. To assess the correlation between fetal NF and gestational age (GA), polynomial equations were calculated and adjusted to determination coefficient (R(2)). RESULTS: The mean fetal NF ranged from 3.98 ± 1.14 mm at 18-18+6 to 4.83 ± 0.93 mm at 24-24+6 weeks of gestation. A good correlation was observed between fetal NF and GA, which is better represented by a linear equation: NF=1.055+0.158*GA (R(2) =0.06). CONCLUSION: Reference intervals of fetal NF thickness measurement in the second trimester of pregnancy were determined for a Brazilian population.

Do clinical practitioners seeking credentialing for nuchal translucency measurement demonstrate compliance with biosafety recommendations? Experience of the Nuchal Translucency Quality Review Program.

OBJECTIVES: The purpose of this study was to evaluate compliance with the ALARA (as low as reasonably achievable) principle by practitioners seeking credentialing for nuchal translucency (NT) measurement between 11 and 14 weeks' gestation. METHODS: Nuchal Translucency Quality Review Program credentialing requires quantitative scoring of 5 NT measurements from 5 different fetuses. Images submitted by 100 consecutive practitioners were retrospectively evaluated for the output display standard (ODS). The thermal index (TI) type (bone [TIb] or soft tissue [TIs]) and numeric value of the index were recorded. The TIb was considered the correct index for this study. Compliance with the numeric value was evaluated in several ways. Collectively, a TIb lower than 0.5 was considered optimal, lower than 0.7 compliant, and 1.0 or lower satisfactory. RESULTS: An ODS was present in at least 1 image submitted by 77 practitioners. The TIb was used exclusively by 15 (19.5%), the TIs by 37 (48.1%), and 25 used a combination of the TIb and TIs. Only 4 of 77 providers (5%) used the correct TI type (TIb) at lower than 0.5 for all submitted images, 5 of 77 (6%) at lower than 0.7, and 9 of 77 (12%) at 1.0 or lower. A TI (TIb or TIs) higher than 1.0 was used by 15 of 77 providers (19.5%). Proficiency in NT measurement and educational background (physician or sonographer) did not influence compliance with ALARA. CONCLUSIONS: Clinicians seeking credentialing in NT do not demonstrate compliance with the recommended use of the TIb in monitoring acoustic output.

The estimation of median nuchal translucency values between 10 and 14 weeks of pregnancy.

Nuchal translucency (NT) is a useful marker in antenatal screening for Down's syndrome in the late first trimester of pregnancy. NT measurements increase with increasing crown rump length (CRL) so multiple of the median (MoM) values are used to allow for this. Log-linear and log-quadratic regressions of NT in relation to CRL have previously been proposed to calculate MoM values. Using data on 288,079 women, these models were compared with a log-sigmoid regression. The log-linear regression overestimated the median NT above a CRL of 75 mm; for example, 1.9 mm versus 1.8 mm observed at 75-79 mm, and 2.0 mm versus 1.8 mm at 80-84 mm. The log-quadratic regression underestimated the median NT below a CRL of 45 mm at 1.03 mm versus 1.2 mm observed. The sigmoid regression provided the best overall fit to the data across the range of CRL values (40-84 mm) corresponding to gestational ages of 76 to 99 days. The differences between the three models are small. If a log-linear regression appears to be a poor fit using local data, a log-sigmoid regression could be considered.

Quality of first-trimester measurement of crown-rump length.

OBJECTIVE: The purpose of this study was to evaluate the quality of crown-rump length (CRL) measurements in scans judged to be of high quality for the measurement of the nuchal translucency. STUDY DESIGN: We analyzed prospective data on 68,250 scans by 1913 sonographers that were collected by the French College of Fetal Echography (CFEF) national practice assessment program for the first-trimester scan. The scans were evaluated according to the CFEF image scoring method (CFEF-ISM), which includes items to measure the quality of the scan for both nuchal translucency and the CRL measurements. The scans were classified into 4 quality groups with the use of the full CFEF-ISM score and then a shortened version of the CFEF-ISM that excluded the item on quality of CRL measurement. The proportion of scans with an inaccurate CRL measurement was compared across the different quality groups. RESULTS: Overall, 21.67% of scans were of insufficient quality for CRL measurement. Among 23,764 "excellent" scans according to the full CFEF-ISM, 965 scans (4.06%) had insufficient CRL quality vs 9.24% of scans with "excellent" quality on the short CFEF-ISM (relative risk, 2.27; 95% confidence interval, 2.11-2.44; P < .001). CONCLUSION: High scores of the quality of nuchal translucency measurement do not guarantee accurate measurement of crown-rump length. Specific measures are needed to evaluate and to improve the quality of the measurement of crown-lump length.

Fetal maxillary and mandibular length in normal pregnancies from 11 weeks' to 13(+6) weeks' gestation: a Taiwanese study.

OBJECTIVES: This study aims to establish the normal range of maxillary and mandibular lengths within the Taiwanese population at 11(+0) weeks to 13(+6) weeks of gestation in normal singleton pregnancy as a reference value for prenatal ultrasonographic examinations. MATERIALS AND METHODS: We examined nuchal translucency in 269 normal singleton pregnancies, with the gestational age ranging from 11 weeks to 13(+6) weeks in this study. Fetal biometric measurements, with an emphasis on maxillary and mandibular lengths, were obtained from the patients during consecutive routine prenatal ultrasonographic examinations. RESULTS: Maxillary and mandibular lengths were recorded successfully in 191 patients and 179 patients, respectively. The mean maternal age was 31 years (range 19-45 years), with a corresponding gestational age of 12 + 4 weeks (range, 11(+0)-13(+6) weeks). A first-degree correlation was found to exist between the gestational age and maxillary length (r = 0.596; p < 0.0001; y = 1.491 × GA - 10.523) as well as mandibular length (r = 0.465; p < 0.0001; y = 1.050 × GA - 6.50). CONCLUSION: Normative data for ultrasonographic measurements of maxillary and mandibular lengths within the Taiwanese population were presented. Our data can serve as a reference value in congenital anomaly screening during prenatal examination.

Impact of gestational age on nuchal fold thickness in the second trimester.

OBJECTIVES: The purpose of this study was to establish gestational age (GA)-specific nomograms for nuchal fold thickness between 16 and 24 weeks. METHODS: This retrospective cross sectional study included 32,207 women who underwent a second-trimester anomaly scan at the Fetal Care Center of National University Hospital from January 2005 to April 2011. Nomograms were plotted for nuchal fold thickness at each gestation to study its variation with GA. RESULTS: Nuchal fold thickness increased with GA in a linear manner from 3.13 ± 0.68 mm (mean ± SD) at 16 weeks to 5.08 ± 0.76 mm at 24 weeks. The 95th percentile measurement at 24 weeks remained less than 6 mm. CONCLUSIONS: A threshold of 6 mm appears to be appropriate for the diagnosis of a thick nuchal fold even for gestations between 20 and 24 weeks.