Nasal bone length throughout gestation: normal ranges based on 3537 fetal ultrasound measurements

Automated Craniofacial Biometry with 3D T2w Fetal MRI

Objectives

Evaluating craniofacial phenotype-genotype correlations prenatally is increasingly important; however, it is subjective and challenging with 3D ultrasound. We developed an automated landmark propagation pipeline using 3D motion-corrected, slice-to-volume reconstructed (SVR) fetal MRI for craniofacial measurements.

Methods

A literature review and expert consensus identified 31 craniofacial biometrics for fetal MRI. An MRI atlas with defined anatomical landmarks served as a template for subject registration, auto-labelling, and biometric calculation. We assessed 108 healthy controls and 24 fetuses with Down syndrome (T21) in the third trimester (29-36 weeks gestational age, GA) to identify meaningful biometrics in T21. Reliability and reproducibility were evaluated in 10 random datasets by four observers.

Results

Automated labels were produced for all 132 subjects with a 0.03% placement error rate. Seven measurements, including anterior base of skull length and maxillary length, showed significant differences with large effect sizes between T21 and control groups (ANOVA, p<0.001). Manual measurements took 25-35 minutes per case, while automated extraction took approximately 5 minutes. Bland-Altman plots showed agreement within manual observer ranges except for mandibular width, which had higher variability. Extended GA growth charts (19-39 weeks), based on 280 control fetuses, were produced for future research.

Conclusion

This is the first automated atlas-based protocol using 3D SVR MRI for fetal craniofacial biometrics, accurately revealing morphological craniofacial differences in a T21 cohort. Future work should focus on improving measurement reliability, larger clinical cohorts, and technical advancements, to enhance prenatal care and phenotypic characterisation.

Absent or hypoplastic nasal bone: What to tell the prospective parents?

BACKGROUND

Absent or hypoplastic nasal bone (AHNB) on first or second-trimester ultrasonography (USG) is an important soft marker of Down syndrome. However, due to its varied incidence in euploid and aneuploid fetuses, there is always a dilemma of whether to go for invasive fetal testing for isolated AHNB. This study aims to assess outcomes specifically within the context of Indian ethnicity women.

MATERIALS AND METHODS

This was a prospective observational study. All patients who reported with AHNB in the first- or second-trimester USG were included. Genetic counseling was done, and noninvasive and invasive testing was offered. Chromosomal anomalies were meticulously recorded, and pregnancy was monitored.

RESULTS

The incidence of AHNB in our study was 1.16% (47/4051). Out of 47 women with AHNB, the isolated condition was seen in 32 (0.78%) cases, while AHNB with structural anomalies was seen in nine cases (0.22%). Thirty-nine women opted for invasive testing. Six out of 47 had aneuploidy (12.7%), while two euploid cases (4.25%) developed nonimmune hydrops. The prevalence of Down syndrome in fetuses with AHNB was 8.5% (4/47) and 0.42% (17/4004) in fetuses with nasal bone present. This difference was statistically significant (p = .001).

CONCLUSION

The results indicate that isolated AHNB cases should be followed by a comprehensive anomaly scan rather than immediately recommending invasive testing. However, invasive testing is required when AHNB is associated with other soft markers or abnormalities. As chromosomal microarray is more sensitive than standard karyotype in detecting chromosomal aberrations, it should be chosen over karyotype.

Assessing the value of second-trimester nasal bone hypoplasia in predicting chromosomal abnormalities: a retrospective chromosomal microarray analysis of 351 fetuses

PURPOSE

To evaluate the value of fetal nasal bone hypoplasia and other prenatal risk factors in predicting chromosomal abnormalities.

METHODS

In this retrospective cohort study, we collected data on singleton pregnancies diagnosed with fetal nasal bone hypoplasia during second-trimester ultrasound. Fetal karyotyping and chromosomal microarray analysis (CMA) were performed, and pregnancy outcomes were assessed. The association between fetal nasal bone hypoplasia and chromosomal abnormalities was evaluated according to whether other prenatal risk factors were observed.

RESULTS

Our final analysis included 351 pregnancies, of which 62 (17.7%) fetuses had chromosomal abnormalities, including 36 cases of trisomy-21, six cases of trisomy-18, one case each of trisomy-13, and 47, XYY syndrome, and 18 cases of copy number variations (CNVs). Among the 243 cases of isolated nasal bone hypoplasia, 28 (11.5%) cases of chromosomal aberrations were identified. The incidence was significantly higher if other soft markers or structural abnormalities were simultaneously detected. Pregnancy was terminated in 43 aneuploid fetuses and nine fetuses detected with CNVs. The parents of the fetuses diagnosed with 47, XYY syndrome and the other nine CNVs chose to continue the pregnancy, and no abnormalities were detected in the newborns. Furthermore, we found that other prenatal risk factors should be considered in evaluating the likelihood of chromosomal abnormalities in fetuses with nasal bone hypoplasia.

CONCLUSIONS

Nasal bone hypoplasia is a highly specific soft marker that is associated with multiple chromosomal abnormalities. The risk of chromosomal abnormalities increases when combined with structural abnormalities or increased nuchal translucency (NT). Chromosomal microarray analysis is a powerful prenatal test for chromosomal abnormalities, which may be warranted in fetuses with nasal bone hypoplasia.

Role of Sonographic Second Trimester Soft Markers in the Era of Cell-Free DNA Screening Options: A Review

Soft markers are sonographic structural, nonspecific signs with little pathological significance, often transient, usually considered as normal variants. However, they may also be associated with chromosomal abnormalities. The most widely examined soft markers include absent or hypoplastic nasal bone (NB), intracardiac echogenic focus (IEF), ventriculomegaly (VM), thickened nuchal fold (NF), choroid plexus cyst (CPC), echogenic bowel, short long bones, and urinary tract dilation (UTD). Although the use of noninvasive prenatal testing (NIPT) has been spreading quickly in maternal–fetal medicine, it is not a diagnostic test and it still remains unavailable or cost-prohibitive for most of the population in many countries. After normal screening test results in the first trimester, there is no uniform consensus regarding the clinical significance of isolated soft markers for aneuploidy. Nowadays, the search for soft markers in an ultrasound is still part of clinical evaluation, and the interpretation of these findings is often a matter of debate. In the present review, we summarize the recent literature about the role of soft markers in the era of NIPT and propose an overview of the different clinical guidelines.

Prenatal sonographic findings in confirmed cases of Wolf-Hirschhorn syndrome

Background

Wolf-Hirschhorn syndrome (WHS) is a common genetic condition and prenatal diagnosis is difficult due to heterogeneous expression of this syndrome and rather non-specific ultrasound findings. Objective of this study was to examine the prenatal ultrasound findings in fetuses with Wolf-Hirschhorn syndrome (WHS).

Methods

Retrospective assessment of 18 pregnancies that were seen at three tertiary referral centers (Universities of Bonn, Tuebingen and Nuernberg / Germany). Findings of prenatal ultrasound examinations, genetic results and outcome were compared. Additionally, findings of our study were compared to previous small case series from the literature and then compared to data on postnatal frequencies and abnormalities in affected patients.

Results

Median gestational age at the time of examination was 23 + 1 weeks’ (range: 13 + 4 to 29 + 1 weeks’) with female-to-male ratio of > 2.5:1. Most frequent ultrasound findings were facial abnormalities, symmetric IUGR and microcephaly that presented in 94.4, 83.3 and 72.2% of cases, respectively. The combination of microcephaly and hypoplastic nasal bone was a particularly characteristic finding. Growth retardation presented in all fetuses > 20 weeks, but not below. Other frequent abnormalities included cardiac anomalies in 50 and single umbilical artery (SUA) in 44.4% of fetuses.

Conclusion

WHS should be considered in the presence of symmetric IUGR together with microcephaly, hypoplastic nasal bone and facial abnormalities on prenatal ultrasound. Genetic testing by chromosomal microarray analysis (CMA) is strongly recommended in this context.

Fetal Nasal Bone Hypoplasia in the Second Trimester as a Marker of Multiple Genetic Syndromes

Nasal bone hypoplasia is associated with a trisomy of chromosome 21, 18 or 13. Nasal bone hypoplasia can also be seen in other, rarer genetic syndromes. The aim of the study was to evaluate the potential of nasal bone hypoplasia, in the second trimester of pregnancy, as a marker of fetal facial dysmorphism, associated with pathogenic copy number variation (CNV). This retrospective analysis of the invasive tests results in fetuses with nasal bone hypoplasia, after excluding those with trisomy 21, 18 and 13. In total, 60 cases with nasal bone hypoplasia were analyzed. Chromosomal aberrations were found in 7.1% of cases of isolated nasal bone hypoplasia, and in 57% of cases of nasal bone hypoplasia with additional malformations. Additionally, in four of nine cases with non-isolated nasal bone hypoplasia but normal CMA results, a monogenic disease was diagnosed. Non-isolated hypoplastic nasal bone appears to be an effective objective marker of fetal facial dysmorphism, associated with pathogenic CNVs or monogenic diseases. In isolated cases, chromosomal microarray testing can be of additional value if invasive testing is performed, e.g., for aneuploidy testing after appropriate counseling.

Reference standards for facial measurements in early third trimester South African fetuses, and the effect of maternal and fetal characteristics

Fetal alcohol spectrum disorder (FASD) is a major problem worldwide and dysmorphic facial features may be a prenatal biomarker for FASD. Deviations from normal facial development cannot be explored before establishing the normal variation in a specific population, since ethnic differences may exist.Objectives: Main objective: to establish reference standards for 23 facial measurements on 3D ultrasound volumes obtained between days 196 and 224 of gestation in healthy unexposed South African fetuses from an area with historically high alcohol consumption prevalence and a population group with no existing normative values. Secondary objective: to assess the confounding effect of maternal and fetal characteristics.Design: This study involves 97 women (including 43 smokers) who had been enrolled in the Safe Passage Study (SPS), a large prospective multinational cohort study assessing the effects of prenatal alcohol exposure. They had adequate 3 D ultrasound volumes of the fetal face acquired at 28⁺⁰-31⁺⁶weeks in singleton pregnancies without comorbidities, congenital abnormalities or exposure to alcohol, marijuana, or methamphetamines from 4 weeks before conception.Participants, materials, setting, methods: The participants were recruited from two residential areas of low socioeconomic status in Cape Town. Meticulous information was collected on maternal and pregnancy characteristics, including alcohol use at different time points. Gestational age (GA) was based on ultrasound biometry before 24 weeks, and 3D ultrasound volumes were acquired trans-abdominally from a sagittal and axial plane of the fetal face. Volumes were independently assessed offline by two observers and the image with the best landmark definition was used for 23 facial measurements, representing features previously described in children with FASD. The relation to the exact GA was assessed by regression analysis, the expected mean value and standard error of the estimate (SEE) was determined to transform all raw measurements into z-scores, and the effect of possible confounders on z-scores was assessed by ANOVA.Results: Ten variables changed significantly with advancing GA (extraocular diameter, anteroposterior, medio-lateral and supero-inferior ocular diameter, ocular volume, interlens distance, prenasal thickness, nasal bone length, nose length and nose protrusion) and thirteen did not (interocular distance; interocular: extraocular diameter ratio, prenasal thickness: nasal bone length ratio, pronasal-subnasal distance, subnasal-mouth distance, philtrum length, upper vermillion thickness, nose-philtrum angle, maxillary angle, facial height, facial protrusion, frontomaxillary facial angle and maxilla-nasion-mandible angle). Reference values (expected mean and SEE) for the 23 measurements were established for each day.The z-scores of all facial measurements were not independently affected by maternal age, parity, gravidity, smoking or body mass index, but infant sex and birthweight z-score significantly influenced several z-scores (infant sex for extraocular, medio-lateral, and supero-inferior ocular diameter, ocular volume, prenasal thickness and nose protrusion; birthweight z-score for extraocular diameter, interocular and interlens distance, nose protrusion and maxillary angle).Limitations: GA was not always confirmed by first trimester ultrasound and some measurements could not be obtained in all cases due to suboptimal image quality. The cohort included few heavy smokers so an effect of heavy or continued smoking cannot be ruled out, and the effect of ethnicity was not assessed.Conclusions: These are the first local reference standards for fetal facial measurements and, to our knowledge, the first reference standards for the supero-inferior ocular diameter, face protrusion, upper vermillion thickness, maxillary angle, and nose-philtrum angle. They were broadly in keeping with published references, with small discrepancies explained by minor differences in technique. Even in this narrow GA window, the distribution of many variables changed over time and normal variation was significantly influenced by fetal sex and birthweight z-score. The possible confounding effect of these factors needs to be considered when assessing the impact of harmful exposures like alcohol on facial development.

Is Prenatal Diagnosis Necessary for Fetal Isolated Nasal Bone Absence or Hypoplasia?

Purpose

This study aimed to explore the value of chromosomal microarray analysis (CMA) and whole exome sequencing (WES) in the prenatal diagnosis of fetal isolated nasal bone absence (INBA) or isolated nasal bone hypoplasia (INBH). We hope to provide additional relevant information for clinical counseling.

Patients and Methods

From November 1, 2018, to March 1, 2020, 55 pregnant women with isolated nasal bone dysplasia were admitted to the Changzhou Maternity and Child Health Care Hospital. Based on the degree of abnormality, the patients were divided into two groups: INBA and INBH. CMA was performed on all patients. The clinical data and prenatal genetic diagnoses of the two groups were retrospectively analyzed. According to the requirements of WES for samples, 12 cases with negative CMA results were selected for the WES test.

Results

A total of 55 cases with INBA or INBH met the inclusion criteria. In 35INBA fetuses, there was one case of trisomy 21 and one case of 10q11.22 deletion (5.7Mb), and the abnormality rate was 5.71% (2/35). Compared with INBA fetuses, the abnormality rate was increased in the fetuses with INBH [15.00% (3/20)] (15.00% vs 5.71%); there was one case of 1q21.1 duplication (1.3Mb), one case of Xp22.31 duplication (1.67Mb), and one case of 4p deletion (7.6Mb). In a later retrospective study, two pathogenic variants were identified in two cases after the WES test; the abnormality rate was 16.67% (2/12), which involved RUNX2 and CDH4 genes, respectively.

Conclusion

A preliminary study confirmed that molecular prenatal diagnosis should be performed in fetuses with INBA or INBH. CMA followed by WES is an effective method.

Fetal Nasal Bone Length in the East African Population

OBJECTIVES

To establish normal ranges of fetal nasal bone length throughout gestation in the East African population and to subsequently compare these measurements with the standardized reference.

METHODS

A retrospective cross-sectional study was performed at the University of Minnesota from January 2011 to December 2016. Fetal nasal bone length measurements were generated in a midsagittal plane at an angle of insonation of 45° from ultrasound images of 1407 nonanomalous fetuses of 1130 mothers of East African decent between 14 and 40 weeks' gestation. The proportion of fetal nasal bone lengths of less than 5.2 mm at week 20 of gestation in the East African population was then compared with the 5% noted by the standardized reference by a χ² test.

RESULTS

The fetal nasal bone length increased linearly with advancing gestational age in fetuses of East African mothers (R² = 0.53; P < .0001). The fetal nasal bone lengths of the East African fetuses were found to be shorter at all ages of gestation compared with the standard reference. At 20 weeks' gestation 17% (95% confidence interval, 13%-22%) of the nasal bone lengths of the East African fetuses were less than 5.2 mm compared with 5% of white and African American fetuses.

CONCLUSIONS

Using the standard reference may lead to a greater than 3.5-fold overdiagnosis of hypoplastic nasal bones in the East African population. To improve aneuploidy risk stratification and patient counseling in the East African population, the introduction of a standardized East African-based fetal nasal bone length reference seems warranted.

Mid-Second Trimester Measurement of Nasal Bone Length in North Indian Population

Objective:

Our objective for this study was to establish a reference range of normal fetal nasal bone length (NBL) from 14 to 22 weeks in a North Indian population.

Materials and Methods:

Pregnant women with gestational age (GA) from 14 to 22 weeks undergoing ultrasonography with a single live fetus and no complications in the fetus or mother were selected for the study. The fetal nasal bone was measured in 2060 pregnant women from 2014 to 2018. The measurement was done by the double operator method; three measurements were taken for each woman when her fetus was in the midsagittal plane, and the nasal bone was located between a 45 and 135° angle to the ultrasound beam. We performed follow-up evaluations of all neonates.

Results:

The rate of growth of the fetal nasal bone during different weeks of gestation is described by an equation where NBL =0.365×GA+ 2.5885, with a fit estimate of R² = 0.97, P < 0.001. The median NBL increased with GA from 2.9 mm at 14 weeks to 5.8 mm at 22 weeks in a linear relationship. Our results in the North Indian population are similar to those in the South Indian population and differ from those in Chinese and Japanese populations.

Conclusions:

The NBL in North Indian fetuses at 14–26 weeks of GA has a linear relationship to the week of gestation.

The complementary role of imaging modalities in Binder phenotype. Can prognostic factors of neonatal respiratory distress be found?

OBJECTIVE

To evaluate the complementarity between prenatal ultrasound, computed tomography, and MRI scans for fetuses with Binder phenotype.

METHODS

We carried out a retrospective study from January 1, 2009, to June 30, 2018, of fetuses with Binder phenotype. Prenatal ultrasound (US) data were collected. A systematic survey of the entire skeleton was performed to look for associated abnormalities such as calcifications, brachytelephalangy, and spinal stenosis. Parents were systematically offered fetal skeletal computed tomography (CT).

RESULTS

Thirteen cases were included. Two cases of perinatal respiratory distress (18%) were observed. Chondrodysplasia punctata was diagnosed from the presence of calcifications, especially of the proximal femoral epiphyses and tarsal bones, in five cases (38%) by US and in 10 cases (83%) by CT. Calcifications of the hyoid bone were detected by CT in three cases (25%) one of which had respiratory distress. Polyhydramnios was associated with the Binder phenotype in four cases (30%) one of which had respiratory distress. One single fetus had combined polyhydramnios and laryngeal calcifications, and he suffered from perinatal respiratory distress.

CONCLUSION

An antenatal diagnosis of Binder phenotype is often associated with chondrodysplasia punctata. We recommend the use of fetal CT as a complement to US in this condition.

Hypoplastic nasal bone: A potential marker for facial dysmorphism associated with pathogenic copy number variants on microarray

OBJECTIVES

To compare the frequency of abnormal genetic diagnoses spanning a period before and after the availability of chromosomal microarray analysis (CMA). We hypothesised that microarray would provide additional clinically relevant information in cases of isolated hypoplastic nasal bone.

METHOD

Fetuses with ultrasound-detected hypoplastic nasal bone (absent or <2.5th percentile in length) between 16 and 37 weeks' gestation over a 10-year period were analysed retrospectively.

RESULTS

A total of 118 cases of hypoplastic nasal bone met the inclusion criteria. A pathogenic or potentially pathogenic karyotype was detected more frequently in the era where CMA was available (31/60, 52% vs 19/58, 33%). Of these, 25 cases (42%) had common aneuploidies, and six cases (10%) had clinically relevant copy number variants (CNVs). A clinically relevant CNV was detected in two fetuses that presented with isolated hypoplastic nasal bone on initial ultrasound.

CONCLUSION

In addition to its known association with trisomy 21, a hypoplastic nasal bone may be an objective marker of facial dysmorphism associated with clinically relevant CNVs. Our results support consideration of invasive testing with microarray for pregnancies in which a hypoplastic nasal bone has been diagnosed on ultrasound irrespective of a low-risk screening result for common chromosomal abnormalities.

Fetal Nasal Bone Length as a Novel Marker for Prediction of Adverse Perinatal Outcomes in the First-Trimester of Pregnancy

Background:

Adverse outcomes of pregnancy are a challenging health-care problem. Prediction of adverse pregnancy outcomes is important to prevent the morbidities of the foetus and the mother.

Aims:

To study the clinical interest of fetal nasal bone length in predicting adverse pregnancy outcomes in the first trimester of pregnancy.

Study Design:

A population-based retrospective cohort study.

Methods:

Data from 868 women with first-trimester fetal nasal bone length and birth records available were enrolled. Fetal nasal bone length percentiles were determined and evaluated for their ability to predict adverse pregnancy outcomes such as preterm birth, preterm labour, preterm premature rupture of membranes, early preterm birth, gestational diabetes mellitus, gestational hypertension-preeclampsia, small-for-gestational age foetuses, macrosomia, oligohydramnios, polyhydramnios and fetal distress.

Results:

Fetal nasal bone length >95^th percentile was significantly associated with preterm labor and preterm premature rupture of membranes (p=0.02, accuracy 0.91 and p=0.001, accuracy 0.94, respectively), whereas nasal bone length >99^th percentile was significantly associated with preterm labor and oligohydramnios (p=0.006, accuracy 0.95 and p=0.014, accuracy 0.97).

Conclusion:

Fetal nasal bone length at high percentiles in the first trimester of pregnancy may aid in the prediction of adverse outcomes such as preterm labour, preterm premature rupture of membranes and oligohydramnios.

Absent fetal nasal bone in the second trimester and risk of abnormal karyotype in a prescreened population of Chinese women

INTRODUCTION

The aim of this study was to evaluate the value of absent fetal nasal bone in the prediction of fetal chromosomal abnormalities, according to whether it was associated with other soft markers or structural abnormalities in a prescreened population of Chinese pregnant women.

MATERIAL AND METHODS

In this retrospective cohort study, women whose fetuses had absent nasal bone detected during the second trimester ultrasound scan were followed. Fetal karyotyping was performed and pregnancy outcomes were recorded. The association between absent fetal nasal bone with abnormal karyotype was evaluated according to whether soft markers or structural abnormalities were also observed.

RESULTS

Fetal nasal bone was assessed in 56 707 singleton pregnancies. After exclusion of unqualified cases, 71 (71/56 707, 0.13%) fetuses were included in the final analyses, of which 16 (16/71, 22.54%) were detected to have chromosomal abnormalities, including 12 cases of trisomy-21, three of trisomy-18, and one of micro-deletion (in 7q). Among the 42 cases with isolated absence of nasal bone, two had trisomy-21 and one had a micro-deletion. Absence of nasal bone in association with other structural abnormalities had a higher rate of abnormal karyotypes compared with isolated absence of nasal bone [83.33% (10/12) vs. 7.14% (3/42), Fisher's exact test χ²  = 25.620, p < 0.001].

CONCLUSION

Absent fetal nasal bone is a highly specific ultrasonographic soft marker that should be included in the routine second trimester ultrasound scan.

Reference ranges for foetal nasal bone length, prenasal thickness, and interocular distance at 18 to 24 weeks' gestation in low-risk pregnancies

Background

The aim of the present study was to establish the normal ranges for foetal nasal bone length (NBL), prenasal skin thickness (PNT), interocular distance (IOD), and ratio of prenasal thickness to- nasal bone length (PNT/ NBL) at 18–24 weeks using two-dimensional (2D) ultrasound.

Methods

This study was a retrospective study of prenatal ultrasonographic records from 407 foetuses between 18 and 24 weeks gestational age (GA). The NBL, PNT, IOD, PNT/ NBL ratio, biparietal diameter (BPD), and femur length (FL) were investigated. The relationships among NBL, PNT, IOD, PNT/ NBL, and GA were evaluated. Additionally, descriptive statistics for NBL, PNT, and IOD values for each gestational week were obtained.

Results

There was a significant association between GA and NBL, PNT, and IOD between 18 and 24 weeks. NBL increased from a mean of 5.5 mm to 8.3 mm, PNT increased from a mean of 3.5 mm to 5.1 mm, and IOD increased from a mean of 11.1 mm to 14.5 mm. PNT/NBL ratio did not change with gestational age.

Conclusions

This study showed normal ranges for NBL, PNT, IOD, and PNT/ NBL ratios for foetuses between 18 and 24 weeks in low-risk pregnancies. There was a positive linear relationship between GA and NBL, PNT, and IOD. The PNT/NBL ratio might be a more useful measurement than NBL or PNT alone.

Electronic supplementary material

The online version of this article (10.1186/s12884-017-1602-3) contains supplementary material, which is available to authorized users.

Screening performance of different methods defining fetal nasal bone hypoplasia as a single and combined marker for the detection of trisomy 21 in the second trimester

OBJECTIVE

To evaluate different methods of defining fetal nasal bone hypoplasia in the second trimester for the detection of trisomy 21.

METHODS

Prospective study in Greek women undergoing anomaly scan between 18 + 0 and 23 + 6 weeks. The following methods of defining nasal bone hypoplasia were evaluated, either as a single marker or in combination with others: (1) BPD to nasal bone length (NBL) ratio; (2) multiples of the median (MoM) of NBL, according to normal curves from a Greek population; (3-4) NBL < 2.5 percentile according to normal curves (3) commonly used internationally curves and (4) curves from a Greek population.

RESULTS

In total, 1301 singleton fetuses were evaluated - 10 with trisomy 21. The best detection rate of trisomy 21 was achieved when the applied method was nasal bone percentiles adjusted to maternal ethnicity, in combination with other markers (<2.5 percentile according to normal curves from a Greek population; p < 0.001; sensitivity 50%; specificity 94.8%; false-positive rate 5.2%; positive likelihood ratio 9.6).

CONCLUSION

Screening performance of fetal nasal bone hypoplasia in detecting trisomy 21 varies according to the method applied. The best screening performance is achieved by using percentiles adjusted to maternal ethnicity in combination with other markers of aneuploidy.

[News methods for second trimester screening of Down syndrome: statistical analysis of the use of nasal bone length and prenasal thickness]

INTRODUCTION

Sonographic measurements of nasal bone length and prenasal soft tissue thickness are ultrasonographic methods for prenatal screening of Down syndrome.

AIM

The aim of the authors was to create a local normogram for nasal bone length and prenasal soft tissue thickness measurements and to test the performance of different statistical methods.

METHOD

Euploid (N = 1500) and trisomy 21 foetuses (N = 10) studied between April 2008 and December 2013 were included. Nasal bone length and prenasal thickness measurements were performed at the Medisono Fetal and Maternal Health Research Centre, Szeged, and cytogenetic tests were performed at the Department of Medical Genetics, University of Szeged, Hungary. Normograms were created with different number of patients (N = 100, 300, 500, 750. 1000 and 1500) and using 3 different statistical methods (linear regression, square-based regression, and box-plot analysis).

RESULTS

The results indicated that at least 1000 measurements are strongly recommended for the normograms. The increase of patient number improved the efficacy of the normograms in each of the 3 statistical methods used for analysis. In general practice box-plots provides a better performance over the other screening methods. However, advanced level screening requires local linear normograms for the best screening results.

CONCLUSION

The use of box-plots is recommended for the use in the daily practice but regression-based normograms are necessary for advanced prenatal screening.

Systematic review and meta-analysis of performance of second-trimester nasal bone assessment in detection of fetuses with Down syndrome

OBJECTIVE

To review systematically the literature on diagnostic tests and performance of second-trimester sonographic assessment of nasal bone (NB) in identifying fetuses affected by Down syndrome.

METHODS

A search of studies involving screening tests for NB evaluation and measurements was carried out in the main international bibliographic databases (MEDLINE, EMBASE and CINAHL). Those considered to be relevant were then subjected to critical reading, following Critical Appraisal Skills Programme (CASP) criteria, by at least three independent observers. All data were extracted and tabulated by two independent investigators. A statistical synthesis of sensitivity, specificity and likelihood ratios was performed using specific software (Meta-DiSc).

RESULTS

From an initial list of 852 articles referring to ultrasound markers for Down syndrome, 207 relevant papers were selected. Following exclusions, 21 studies were included in the quantitative synthesis. The pooled estimates of positive and negative likelihood ratios were 40.08 (95% CI, 18.10-88.76) and 0.71 (95% CI, 0.64-0.79), respectively, for absent NB and 15.15 (95% CI, 8.15-28.16) and 0.47 (95% CI, 0.34-0.64), respectively, for hypoplastic NB. No relevant differences were found between the various means of defining nasal hypoplasia (multiples of the median (MoM) or percentiles). The biparietal diameter/nasal bone length (BPD/NBL) ratio showed somewhat higher sensitivity but lower specificity with a threshold effect.

CONCLUSIONS

NB absence or hypoplasia show high specificity and low but acceptable sensitivity in identifying fetuses with Down syndrome. Screening performance is better with NB measurements as a function of MoM or percentiles rather than as the BPD/NBL ratio. Classification of women into various risk groups for Down syndrome does not affect diagnostic performance.

Fetal nasal bone length during the second trimester of pregnancy in a Turkish population

OBJECTIVE

To determine the distribution of fetal nasal bone length (NBL) according to gestational age during the second trimester of pregnancy in a Turkish population.

STUDY DESIGN

Fetal NBL and other routine biometric measurements were evaluated retrospectively in 2327 fetuses between 15 and 24 weeks of gestation. The measurements were obtained via transabdominal ultrasound. The distribution of fetal NBL between 15 and 24 weeks of gestation was established, and percentiles were calculated. Relationships between fetal NBL and other parameters were assessed using regression analysis.

RESULTS

Mean (±standard deviation) fetal NBL ranged from 2.95±0.52 at 15 weeks of gestation to 6.26±0.77mm at 24 weeks of gestation. The fifth percentile for fetal NBL was 2.1mm at 15 weeks of gestation and 5.0mm at 24 weeks of gestation. A significant positive correlation was noted between fetal NBL and gestational age (NBL=gestational age×0.37-2.55; R(2)=0.59; p<0.01) and between fetal NBL and biparietal diameter (BPD) (NBL=BPD×0.11-0.33; R(2)=0.61; p<0.01).

CONCLUSION

Fetal NBL is less in Turkish subjects compared with non-Turkish subjects.

Nasal bone length: the long and short of it. Evaluation of the reference values for the fetal nasal bone length at 16 to 25 weeks of gestational age in an Indian population

OBJECTIVE

To establish a reference interval range for the fetal nasal bone length (NBL) in an Indian population.

METHODS

A retrospective study of antenatal ultrasound records of fetuses at 16 to 25 weeks in singleton pregnancies. NBL, biparietal diameter (BPD) and femur length were noted in 6436 observations of singleton, euploid, nonmalformed pregnancies.

RESULTS

The 50th centile for NBLs increased from 3.4 to 6.9 mm from 16th to 25th week of gestational age. The relation between nasal bone and gestational age, BPD and femur length were found and noted. The NBLs were found to be shorter when compared with other ethnicities.

CONCLUSIONS

A reference range for fetal NBLs at 16 to 25 weeks in an Indian population and its relation with fetal biometry was established.

Nasolabial dimensions of the facial profile at 20 to 37 weeks' gestation on 2- and 3-dimensional sonography in normal Korean fetuses

OBJECTIVES

The purpose of this study was to evaluate normal nasolabial dimensions using the images of facial profiles in normal Korean fetuses.

METHODS

We conducted a cross-sectional study of 355 normal fetuses at 14 to 39 weeks' gestation. After the exclusion of inadequate images and inadequate numbers of fetuses at 14 to 19 and 37 to 39 weeks' gestation, the sonographic facial profiles from 222 fetuses at 20 to 37 weeks' gestation were evaluated. Five parameters, nose length, nose protrusion, pronasal-subnasal distance, distance between the upper philtrum and mouth, and distance between the tip of the nose and mouth, were measured and are presented according to gestational age. Data were analyzed by intraclass correlation coefficients and regression analysis.

RESULTS

There were significant linear correlations between gestational age and nose length (R = 0.390; P < .001), pronasal-subnasal distance (R = 0.415; P < .001), and distance between the upper philtrum and mouth (R = 0.315; P < .001). There were significant quadratic relationships between gestational age and nose protrusion (R(2) = 0.213; P < .001) and distance between the tip of the nose and mouth (R(2) = 0.173; P < .001).

CONCLUSIONS

We provide preliminary normative nasolabial dimensions of facial profiles at 20 to 37 weeks' gestation in normal Korean fetuses. These data may be of help not only in the understanding of normal nasolabial growth in utero but also in the diagnosis of abnormal facial dimensions.

Three-dimensional ultrasonography measurement of fetal nasal bone length during the midtrimester in Taiwanese women

OBJECTIVE

To evaluate the normal range of the fetal nasal bone length (NBL) in Taiwanese women using three-dimensional (3D) ultrasound, and compare the NBL of normal fetuses with Down syndrome to determine its significance in screening for trisomy 21.

MATERIALS AND METHODS

A total of 102 consecutive fetuses and another 7 fetuses with trisomy 21, determined by karyotyping at 15-22 weeks' gestation, were evaluated with 3D ultrasound before amniocentesis at Changhua Christian Hospital between November 2003 and April 2004.

RESULTS

The normal range for NBL in the second trimester in the Taiwanese population was investigated, and a linear relationship with gestational age was noted. The NBL increased with advancing gestational age (NBL in cm=0.0264×gestational age in weeks -0.042 (R(2)=0.2416). The median of the biparietal diameter/nasal bone length ratio had a stable value which tended to change minimally between 15 and 22 weeks of gestation. Chromosomally normal fetuses had statistically longer nasal bones than fetuses with Down syndrome (p=0.014).

CONCLUSION

We present a reference range for 3D ultrasound measurement of the fetal NBL. A short nasal bone at 15 to 22 weeks is associated with a high risk of trisomy 21.

Mid-second Trimester Measurement of Nasal Bone Length in the Indian Population

OBJECTIVE

The purpose of this study was to establish an Indian reference for normal fetal nasal bone length at 16-26 weeks of gestation.

METHODS

The fetal nasal bone was measured by ultrasound in 2,962 pregnant women at 16-26 weeks of gestation from 2004 to 2009 by a single operator, who performed three measurements for each woman when the fetus was in the midsagittal plane and the nasal bone was between a 45 and 135° angle to the ultrasound beam. All neonates were examined after delivery to confirm the absence of congenital abnormalities.

RESULTS

The median nasal bone length increased with gestational age from 3.3 mm at 16 weeks to 6.65 mm at 26 weeks in a linear relationship. The fifth percentile nasal bone lengths were 2.37, 2.4, 2.8, 3.5, 3.6, 3.9, 4.3, 4.6, 4.68, 4.54, and 4.91 mm at 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, and 26 weeks, respectively.

CONCLUSIONS

We have established the nasal bone length in South Indian fetuses at 16-26 weeks of gestation and there is progressive increase in the fifth percentile of nasal bone length with advancing gestational age. Hence, gestational age should be considered while defining hypoplasia of the nasal bone.

Three-dimensional ultrasound imaging and measurement of nasal bone length, prenasal thickness and frontomaxillary facial angle in normal second- and third-trimester fetuses

OBJECTIVES

To assess the feasibility of nasal bone length (NBL), prenasal thickness (PT) and frontomaxillary facial (FMF) angle measurements performed on the same three-dimensional (3D) multiplanar-corrected profile view in healthy second- and third-trimester fetuses, to create reference ranges and to review published measurement techniques.

METHODS

3D volumes of 219 healthy second- and third-trimester fetuses were retrospectively analyzed. The quality of images and measurability of the markers were assessed with 5-point and 3-point scoring systems, respectively. Measurements of NBL (with care to exclude the frontal bone), PT and FMF were obtained in the exact mid-sagittal plane. Reference ranges were constructed based on measurements from images with high-quality (4 or 5 points) and high measurability (2 or 3 points) scores and compared with those in the most relevant published literature.

RESULTS

A high-quality score was assigned to 111 images. Among these, a high measurability score was significantly more often achieved for NBL (98.2%) and PT (97.3%) than for the FMF angle (26.1%) (P < 0.001). Both NBL (NBL = - 6.927 + (0.83 × GA) - (0.01 × GA(2))) and PT (PT = (0.212 × GA) - 0.873) (where GA = gestational age) showed growth with gestation, with less pronounced growth for NBL after 28 weeks. Our reference range for the NBL showed a systematically smaller length than those in other two-dimensional (2D) ultrasound-based publications. The FMF angle measurements that we obtained did not show a significant change with GA.

CONCLUSIONS

NBL and PT are easily measured using 3D ultrasound whereas FMF angle measurement is more challenging. When it is measured in the exact mid-sagittal plane and care is taken to exclude the frontal bone, measurements of the NBL are systematically smaller than those in previous 2D ultrasound-based publications.

Prenasal thickness-to-nasal bone length ratio: a strong and simple second- and third-trimester marker for trisomy 21

OBJECTIVES

To study the ratio of prenasal thickness (PT) to nasal bone length (NBL) in normal and trisomy-21 fetuses in the second and third trimesters of pregnancy.

METHODS

The PT and NBL were measured retrospectively in 106 normal fetuses (in three-dimensional (3D) volumes) and in 30 fetuses with trisomy 21 (10 on two-dimensional (2D) images and 20 in 3D volumes).

RESULTS

In normal fetuses the mean PT and NBL increased between 15 and 33 weeks' gestation from 2.3 to 6.1 mm (r = 0.85, P < 0.001) and from 3.3 to 9.6 mm (r = 0.87, P < 0.001), respectively. The PT : NBL ratio was stable throughout gestation, with a mean of 0.61 (95% CI, 0.59-0.63; r = - 0.04, P = 0.7). The 5(th) and 95(th) percentiles were 0.48 and 0.80, respectively. In trisomy-21 fetuses the mean PT and NBL increased between 14 and 34 weeks from 3.0 to 9.2 mm (r = 0.86, P < 0.001) and from 1.9 to 7.8 mm (r = 0.85, P < 0.001), respectively. The PT : NBL ratio was significantly higher than in normal fetuses (P < 0.001) but also stable throughout gestation, with a mean of 1.50 (95% CI, 1.20-1.80; r = - 0.35, P = 0.07). Twenty-three (77%) of the 30 fetuses with trisomy 21 had a PT above the 95(th) percentile and 20 (67%) had an NBL below the 5(th) percentile. All the trisomy-21 fetuses had a PT : NBL ratio above the 95(th) percentile. When the 95(th) percentile of the PT : NBL ratio was used as a cut-off value the detection and false positive rates for trisomy 21 were 100 (95% CI, 89-100)% and 5 (95% CI, 2-11)%, respectively. The positive likelihood ratio was 21.2.

CONCLUSIONS

The PT : NBL ratio is stable in the second and third trimesters of pregnancy in both normal and trisomy-21 fetuses, but all trisomy-21 fetuses in this series had a PT : NBL ratio above the 95(th) percentile. The ratio is therefore a strong marker for trisomy 21.

A Thai reference for normal fetal nasal bone length at 11-13(+6) weeks gestation

AIM

The purpose of this study was to establish a Thai reference for normal fetal nasal bone length (NBL) at 11-13(+6) weeks gestation.

METHODS

The fetal nasal bone was measured by sonography in pregnant women at 11-13(+6) weeks gestation. All neonates who showed normal karyotypes were examined after delivery to confirm the absence of congenital abnormalities.

RESULTS

A total of 255 pregnant women were recruited. Forty-seven pregnant women were excluded from the analysis because of technically unsatisfactory examination or absent nasal bone and chromosomal abnormalities. The mean ± SD of NBL was 1.79 ± 0.33 mm and increased significantly with crown-rump length (CRL) and gestational age (p < 0.001). The best-fit equation for NBL in euploid fetuses in relation to CRL was: NBL (mm) = (0.030 × CRL (mm)) - 0.016.

CONCLUSION

NBL in Thai fetuses at 11-13(+6) weeks was found to be on average shorter than that in Caucasian, African-American and Chinese populations, but similar to those reported in Korean and Latin-American populations.

Normal ranges for fetal nasal bone length determined by ultrasound at 18-20 weeks of gestation in a multiethnic Australian population

OBJECTIVE

Absence or hypoplasia of the nasal bone is commonly reported in Down syndrome fetuses. We define normal ranges and the 2.5th centile for fetal nasal bone length (NBL) in a multiethnic Australian population at 18-20 weeks of gestation.

METHODS

A prospective cohort study of women attending for a routine anomaly scan. Ethnicity of the patient and their partner was recorded, and the nasal bone was measured three times. Two methods of nasal bone assessment were used to define normal ranges: a single (first) measurement and the mean value of three measurements. Mixed-effects regression models were employed to account for interoperator differences treating sonographers as random effects. Nonparametric methods were used to define the 2.5th centile for gestational age.

RESULTS

A total of 1199 women were included with a mean gestational age 19.1 (SD 0.4; range 18-20) weeks. There is significant linear relationship between NBL and gestational age (P<0.001). The mean of three nasal bone measurements had a smaller standard deviation than single nasal bone measurements. Nonparametric assessment was used to define the 2.5th centile, which is 4.4 mm at 18 weeks and 5.0 mm at 20 weeks of gestation.

CONCLUSIONS

This study provides a reference range for fetal NBL at 18-20 weeks of gestation in an unselected multiethnic Australian population. Whilst NBL increases linearly from 18 to 20 weeks, the data are not normally distributed and nonparametric techniques are required to define the 2.5th centile. The mixed-effects model also accounts for variation in sonographer measurements.

Normative values of fetal nasal bone lengths of Turkish singleton pregnancies in the first trimester

OBJECTIVE

Evaluation of nasal bone improves the performance of first-trimester screening for trisomy 21. In this retrospective study we aimed to determine normative values related to the measurement of nasal bone length of the Turkish population during the first trimester ultrasonographic fetal screening.

MATERIAL AND METHODS

Medical records of singleton pregnancies, whose first trimester fetal screening was performed between 2004 and 2010, were evaluated retrospectively. Pregnancies with any detected/suspicious anatomical or genetic fetal anomalies, biochemical abnormalities, increased nuchal translucency measurements, and pregnancies of artificial reproduction techniques were excluded from data analyses. Mean±standard deviation, median and percentile values of the length of nasal bone were calculated separately for 11(0-6), 12(0-6) and 13(0-6) gestational weeks.

RESULTS

Nasal bone could be visualized in 99.6% of the included 1762 singleton pregnancies. In 16.5% of the cases nasal bones were only noted as present or absent. Mean maternal age was 29.67±4.50 years and mean gestational age was 12.54±0.61 weeks. Median values of nasal bone lengths were 1.7, 1.9, and 2.2 mm for 11(0-6), 12(0-6) and 13(0-6) gestational weeks respectively. Nasal bone length (NBL) increased linearly with advancing gestational age and CRL. NBL (mm)=[0.298xGestational Age (week)]-1.779, R(2)=0.318; p<0.001; NBL (mm)= [0.023 × CRL (mm)] + 0.520, R(2)=0.331; p<0.001.

CONCLUSION

The present study presents normative values of nasal bone in the first trimester screening of normal singleton pregnancies of Turkish population. Nasal bone length increases with advancing gestational age and CRL.

First trimester examination of fetal nasal bone in the Turkish population

AIM

The present study aims to assign the reference values for nasal bone length (NBL) screened at 11-14 weeks of pregnancy in the Turkish population, determining whether the NBLs specified for Caucasians can be validated for Turkish people.

MATERIALS & METHODS

The values of NBL were investigated in a total of 415 singleton fetuses that had Turkish parents and normal neonatal outcome. Sonographic measurements of NBL were done on a transabdominal midsagittal plane at 11-14 weeks' gestation. Regression analysis was used to assess the relationship between NBL and crown-rump length (CRL). Reference values, including the 5(th), 50(th) and 95(th)percentiles, were calculated for each gestational age.

RESULTS

The mean NBL was estimated to be 2.5 mm for 11-11 + 6/7 weeks, 2.9 mm for 12-12 + 6/7 and 3.4 mm for 13-13 + 6/7 weeks' gestation. The measurements of NBL showed a significant increase with CRL so that a linear and direct correlation was found between NBL and CRL (NBL = 0.267 + 0.043 x CRL, P < 0.001). Moreover, a significant and linear relationship was detected between NBL and gestational age (NBL = -3.858 + 0.537 x gestational age, P < 0.001).

CONCLUSION

The measurement of NBL is found to be achievable in the majority of first trimester pregnancies. The reference range of NBL in normal Turkish fetuses is established so that basic data can be recorded for further studies related to NBL measurements in screening for various chromosomal abnormalities including Down syndrome within Turkish population.

A prospective cross-sectional study to define racial variation in fetal nasal bone length through ultrasound assessment at 18-20 weeks' gestation

OBJECTIVE

An absent or short nasal bone is highly predictive of Down syndrome in Caucasian populations, but Asians may have shorter nasal bones - increasing the false positive rate of screening. We examine differences in nasal bone length (NBL) in Caucasian and Asian populations.

METHODS

This prospective cohort study involved pregnant women attending for their routine anomaly scan at 18-20 weeks' gestation. Ethnicity of the patient and their partner was recorded, and the nasal bone was measured three times. Mean NBL was calculated and used to investigate the effect of ethnicity first with a simple linear regression model and second with a mixed-effects regression model that accounted for variability of measurement between sonographers.

RESULTS

A total of 1087 families were involved in the study, including 592 (54%) Caucasians, 214 (20%) East Asians, 110 (10%) South Asians and 171 (16%) West Asians. Twenty-three sonographers performed the scans with an average of 19 scans each. There is no significant difference in NBL between Caucasian and Asian populations. The mixed-effects model shows that accounting for sonographer variation is important, with 6.7% of the total variance in measurement being related to this random effect.

CONCLUSIONS

There is no significant difference in NBL between Caucasian and Asian populations. It is reasonable to use criteria established in a Caucasian population to define the characteristics of an absent/short nasal bone in Asian fetuses. This finding also removes difficulties in counselling mixed race couples.

Nasal-bone length in euploid fetuses at 16-24 weeks' gestation by three-dimensional ultrasound

OBJECTIVE

To establish a normal range of nasal-bone length at 16-24 weeks' gestation by the use of three-dimensional (3D) ultrasound and to investigate the effect of deviations from the exact mid-sagittal plane on the measurement of nasal-bone length.

METHODS

We acquired 3D volumes of the fetal profile from 135 normal fetuses at 16-24 weeks' gestation. The multiplanar mode was used to obtain the exact mid-sagittal plane and to produce parasagittal and oblique views of the fetal face. Nasal-bone length was measured in each plane and the sonographic landmarks of each profile view were examined.

RESULTS

Nasal-bone length increased with gestational age from a mean of 4.1 mm at 16 weeks to 7.1 mm at 24 weeks. There was a tendency to underestimate nasal-bone length when the measurements were taken in parasagittal planes and to overestimate the measurements when they were taken in oblique views, compared to the exact mid-sagittal plane. The mean difference in nasal-bone length from the one in the mid-sagittal plane was 0.42 and 0.63 mm for parasagittal measurements at 1 and 2 mm, respectively, from the midline, -0.08 and -0.51 mm for oblique measurements at 10 degrees and 20 degrees rotation along the z-axis and -0.69 mm for rotation of 20 degrees along the z-axis and 10 degrees along the y-axis. The vomeral bone was the only sonographic landmark defining the exact mid-sagittal plane of the face that was not visible in the parasagittal and oblique planes.

CONCLUSIONS

Parasagittal and oblique scanning planes may produce different degrees of under- or over-estimation of nasal-bone length compared to measurements systematically taken in the exact mid-sagittal plane. Inclusion of the vomeral bone in the definition of the exact mid-sagittal plane of the face could improve the reproducibility of measurements of nasal-bone length.

Nuchal fold thickness, nasal bone absence or hypoplasia, ductus venosus reversed flow and tricuspid valve regurgitation in screening for trisomies 21, 18 and 13 in the early second trimester

OBJECTIVE

To investigate the performance of nuchal fold thickness, nasal bone hypoplasia, reversed flow in the ductus venosus and tricuspid valve regurgitation in the prediction of fetal aneuploidies in the early second trimester.

METHODS

This was a prospective study of 870 fetuses at 14 + 0 to 17 + 6 weeks of gestation, performed from 2005 to 2007. In all cases we assessed classical structural anomalies, second-trimester markers of aneuploidy including nuchal fold thickness and nasal bone length, as well as ductus venosus blood flow pattern and tricuspid valve regurgitation.

RESULTS

The study group included 37 fetuses with trisomy 21, eight with trisomy 18 and four with trisomy 13. Nasal bone hypoplasia was the single most sensitive parameter to identify fetuses with trisomy 21. Independent from maternal age, screening by assessment of nuchal fold and nasal bone identified 64.9% of cases with trisomy 21 and 66.7% of cases with trisomy 18/13 (false-positive rate (FPR), 5.8%). By including ductus venosus and tricuspid flow evaluation, the detection rate increased to 75.7% for trisomy 21 and 83.3% for trisomy 18/13 (FPR, 10.8%). Identification of fetuses with structural abnormalities combined with assessment of all four markers under investigation raised the detection rate of trisomy 21 to 83.9% and that of trisomy 18/13 to 100%. The sensitivity of classical second-trimester markers was 62.2% for trisomy 21 and 70.6% for other autosomal aneuploidies (FPR, 11.3%).

CONCLUSION

The combination of assessment of nuchal fold thickness, nasal bone hypoplasia, ductus venosus reversed flow and tricuspid regurgitation in the early second trimester is associated with a higher detection rate of autosomal trisomies compared with classical second-trimester marker screening.

First trimester measurements of nasal bone length using three-dimensional ultrasound

OBJECTIVES

To investigate the feasibility and reproducibility of measurements of nasal bone length using a three-dimensional (3D) ultrasound in the first trimester.

METHODS

In a prospective study, 118 consecutive pregnant women attending for Down syndrome screening at 11-13 + 6 weeks were recruited. They had successful fetal nasal bone measurement by two-dimensional (2D) ultrasound by four operators. Three-dimensional volumes were recorded in the mid-sagittal plane of fetal profile by the fifth operator and examined using multiplanar techniques. Another independent investigator randomly compared his measurements with one of the four operators.

RESULTS

In the subsequent 3D examination, the nasal bone length could be examined in 94 cases (79.7%). The mean difference between the 2D and 3D measurements was 0.19 mm [95% confidence interval (CI) 0.08 to 0.31] (P < 0.05). Limits of agreement were -0.73 to 1.11. The mean differences between these two observers were 0.66 mm (95% CI -0.47 to 0.86) (P < 0.05).

CONCLUSIONS

There was significant intermethod difference between the results obtained by 2D and 3D, as well as substantial interobserver variation in 3D measurement of fetal nasal bone length in the first trimester. Independent 3D measurement of nasal bone offers no additional advantages over 2D sonography.

First-trimester fetal nasal bone length in an ethnic Chinese population

OBJECTIVES

To determine reference ranges of fetal nasal bone length (NBL) in a Chinese population and to assess the value of NBL measurement in screening for chromosomal defects in the first trimester.

METHODS

In this prospective study the fetal profile was examined and the fetal NBL and crown-rump length (CRL) were measured in Chinese women presenting with singleton pregnancies for first-trimester screening for aneuploidy between January 2004 and June 2007. Screening was performed on the basis of nuchal translucency (NT) measurement and maternal serum free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A levels.

RESULTS

NBL was measured in 7543 fetuses, of which 7517 were euploid. The best fit equation for median NBL in euploid fetuses in relation to CRL was: NBL (mm) = 0.4593 + (0.0186 x CRL(mm)). The NBL for gestational age (GA, in days) was given by the equation NBL(mm) = 0.2392 + (0.0027 x GA). There was no correlation between log(10)(NBL multiples of the median (MoM)) and log(10)(NT MoM) in unaffected pregnancies (r = - 0.009; P = 0.43). Only two of the 11 cases with trisomy 21 had an NBL outside the 5(th) or 95(th) centiles of the reference range for euploid fetuses.

CONCLUSION

Reference ranges for NBL in a Chinese population suitable for screening for aneuploidy between 11 and 13 + 6 weeks' gestation have been derived. The NBL in Chinese fetuses is similar to that of other ethnic groups. However, unlike the determination of presence vs. absence of the nasal bone, NBL measurement is unlikely to further improve screening for aneuploidy.

First-trimester nasal bone length in a normal Latin American population

OBJECTIVES

To report normative data of nasal bone length (NBL) in first-trimester singleton fetuses in a normal cohort of Latin American women.

METHODS

NBL was measured during routine first-trimester sonographic examination in 1040 singleton fetuses from an unselected population.

RESULTS

NBL increased linearly with advancing gestational age (GA) [NBL (mm) = - 1.10 + 0.03 x GA (days), R(2) = 0.21; p < 0.001]. Similarly, there was a linear relationship between the NBL and crown-lump length (CRL) [NBL (mm) = 0.41 + 0.02 x CRL (mm), R(2) = 0.27; p < 0.001]. The NBLs at the 50th percentile in our population were 1.5, 1.7, and 1.9 mm at 11, 12, and 13 weeks of gestation, respectively.

CONCLUSIONS

Whereas categorizing a nasal bone as absent or present can be subjective because of variations in echogenicity due to technique and equipment, measurement of NBL is a more objective approach to nasal bone assessment in screening for aneuploidy. Measurement of NBL in the first trimester is feasible and can be easily obtained at the time of nuchal translucency assessment. The normative data we report can provide a reference for defining nasal bone hypoplasia in the first trimester in the Latin American population.

A Thai reference for normal fetal nasal bone length at 15 to 23 weeks' gestation

OBJECTIVE

The purpose of this study was to establish a Thai reference for normal fetal nasal bone length at 15 to 23 weeks' gestation.

METHODS

The fetal nasal bone was measured by sonography in 295 pregnant women at 15 to 23 weeks' gestation from May to August 2005. One of the first 4 authors performed 3 measurements for each woman when the fetus was in the midsagittal plane and the nasal bone was close to a 45 degrees or 135 degrees angle to the ultrasound beam. All neonates were examined after delivery to confirm an absence of congenital abnormalities.

RESULTS

The median nasal bone length increased by gestational age from 3.6 mm at 15 weeks to 7.3 mm at 23 weeks in a linear relationship. The fifth percentile nasal bone lengths were 2.5, 3.04, 3.28, 3.64, 4.21, 4.82, 5.69, and 6.13 mm at 15, 16, 17, 18, 19, 20, 21, and 22 weeks, respectively. The median time for measurement was 5 minutes.

CONCLUSIONS

The nasal bone length in Thai fetuses at 15 to 23 weeks was found to be on average shorter than that in white and African American fetuses.

Fetal nasal bone length and Down syndrome during the second trimester in a Chinese population

OBJECTIVE

The purpose of the present study was to build a database of reference ranges of fetal nasal bone length (NBL) in a Chinese population. The accuracy rate of detecting Down syndrome was also analyzed using fetal NBL as a marker.

METHODS

The control group of fetuses included 342 normal singleton pregnancies with no chromosomal or congenital anomalies. The present study was a cross-section study and the control group was used to construct percentile values of NBL from 13 to 29 gestational weeks of age. Two-dimensional ultrasonography was used for the nasal bone studies. Measurements of NBL were collected and each fetus contributed a single value to the reference sample. During the study period, 14 fetuses with Down syndrome were examined. Measurement of fetal NBL was made during amniocentesis, with gestational age ranging from 13 to 19 weeks.

RESULTS

From 342 normal fetuses with gestational age ranging from 13 to 29 weeks, reference ranges of NBL were constructed. The reference ranges were constructed from the 100(1 - p)% reference range: Y +/- Zp x square root sigma 2, where Y = 25 - exp(3.58 - 0.044 x t + 0.0006 x t2), with Y being the fitted mean of regression model and t being gestational age (weeks). Using fetal NBL, the regression model was Pr(Down syndrome) = exp(W)/ [1 + exp(W)], where W = 0.62-4.80 x NBL (multiples of the median) in predicting Down syndrome. Fetal NBL was found to have a sensitivity and specificity of 0.78 and 0.78, respectively, in predicting Down syndrome in the second trimester of pregnancy.

CONCLUSIONS

Fetal NBL measurement can provide a simple and useful algorithm to predict Down syndrome during the second trimester of pregnancy.

Medida do comprimento do osso nasal entre 11 e 15 semanas de gestação em uma população brasileira: estudo preliminar

OBJETIVO: Determinar valores de referência para o comprimento do osso nasal entre 11 e 15 semanas de gestação em uma população brasileira. MATERIAIS E MÉTODOS: Realizou-se estudo de corte transversal com 171 gestantes normais entre 11 e 15 semanas completas. O osso nasal foi medido por via transabdominal em todos os casos. Foram calculados os percentis 5 a 95 para o comprimento do osso nasal pela fórmula: média ± 1,645 desvio-padrão. Para avaliar a correlação do comprimento do osso nasal com parâmetros antropométricos fetais utilizou-se o coeficiente de correlação de Spearman, com intervalo de confiança de 95%. RESULTADOS: O osso nasal foi mensurado em todos os casos, sendo que o comprimento médio variou de 1,69 mm a 2,94 mm. O comprimento do osso nasal mostrou-se fortemente correlacionado com todos os parâmetros antropométricos fetais (p < 0,001) e com a idade gestacional (R² = 0,59). CONCLUSÃO: Apesar de ser um estudo preliminar, a curva de referência do comprimento do osso nasal foi estabelecida.

Ethnic variation and variability of fetal nasal bone length at 11-15 weeks of gestation in a Brazilian population: preliminary results

OBJECTIVE

To evaluate the maternal ethnic influence and the intra and interobserver reproducibility of the nasal bone length measurement at 11-15 weeks of gestation in a Brazilian population.

METHODS

A cross-sectional study with 171 normal pregnant women at 11-15 weeks was performed. Nasal bone was transabdominally measured in all cases. The patients were separated into three racial groups (White, Black and Asian) according to maternal ethnicity. The intraobserver variability was calculated through the repeated measurement of 55 fetuses by a single observer, and the interobserver variability was calculated through 44 measurements by two observers. The ANOVA test was used to compare the three racial groups. To calculate the variability, the intraobserver correlation coefficient (intra-CC), the interclass correlation coefficient (inter-CC) with 95% confidence interval, and the Bland-Altman plots were used.

RESULTS

No statistically significant difference could be observed among the three races as for nasal bone length measurement (P = 0.934). The intraobserver variability was considered very good [intra-CC 0.92-IC 95% (0.902; 0.947)], as well as the interobserver variability [inter-CC 0.91-IC 95% (0.873; 0.940)].

CONCLUSIONS

There is no significant difference in nasal bone length measurement among the three races analyzed. Nasal bone length measurement is reproducible.

The role of perinatal autopsy in the management of pregnancies with major fetal trisomies

We assessed the value of perinatal autopsy following mid-trimester termination of pregnancy due to major fetal trisomies. Singleton fetuses (n=305) that underwent prenatal sonography and karyotyping during the second trimester of pregnancy and that had trisomy 21, trisomy 18, or trisomy 13 constituted the study population. The findings of second trimester sonography and fetal autopsy were compared. Altogether, 611 separate major structural malformations were diagnosed during autopsy. Full agreement was achieved between sonography and autopsy in 35.8% of the malformations. The additional findings at autopsy (64.2%) involved mainly two organ systems: face, including ears and eyes, and extremities, including hands and feet. Some ultrasound findings were not confirmed at autopsy (n=49). Concordance rates between sonography and autopsy findings regarding soft markers were considerably high in cases of increased nuchal fold thickness and short femur/humerus. On the other hand, fetal autopsy was of limited value as far as hyperechoic bowel and echogenic intracardiac foci are concerned. Pathologic examination provides additional information regarding many fetuses with aneuploidy, and may indicate possible directions of sonographic screening for major chromosome aberrations. However, prenatal sonography and perinatal autopsy should be considered as complementary ways of increasing our knowledge about the possible features of fetal aneuploidies.