Nasal bone assessment in prenatal screening for trisomy 21

Single nucleotide polymorphism array (SNP-array) analysis for fetuses with abnormal nasal bone

PURPOSE

This study aims to evaluate the prevalence of submicroscopic chromosomal abnormalities found on single nucleotide polymorphism array (SNP array) in pregnancies with either an absent or hypoplastic nasal bone.

METHODS

This retrospective study included 333 fetuses with either nasal bone hypoplasia or absence identified on prenatal ultrasound. SNP array analysis and conventional karyotyping were performed in all the subjects. The prevalence of chromosomal abnormalities was adjusted for maternal age and other ultrasound findings. Fetuses with either an isolated nasal bone absence or hypoplasia, those that had additional soft ultrasound markers, and those where structural defects were found on ultrasound were divided into three groups: A, B, and C, respectively.

RESULTS

Among the total cohort of 333 fetuses, 76 (22.8%) had chromosomal abnormalities, including 47 cases of trisomy 21, 4 cases of trisomy 18, 5 cases of sex chromosome aneuploidy, and 20 cases of copy number variations of which 12 were pathogenic or likely pathogenic. The prevalence of chromosomal abnormalities in group A (n = 164), B (n = 79), and C (n = 90) was 8.5%, 29.1% and 43.3%, respectively. The incremental yields by SNP-array compared with karyotyping in group A, B, and C were 3.0%, 2.5% and 10.7%, respectively (p > 0.05). Compared to karyotype analysis, SNP array detected an additional 2 (1.2%), 1 (1.3%), and 5 (5.6%) pathogenic or likely pathogenic CNVs in groups A, B, and C, respectively. In the 333 fetuses, the prevalence of chromosomal abnormalities in women with advanced maternal age (AMA) was significantly higher than that in non-AMA women, (47.8% vs. 16.5%, p < 0.05).

CONCLUSION

In addition to Down's syndrome, many other chromosomal abnormalities are present in fetuses with abnormal nasal bone. SNP array can improve the prevalence of chromosomal abnormalities associated with nasal bone abnormalities, especially in pregnancies with non-isolated nasal bone abnormalities and advanced maternal age.

Prenatal diagnosis of fetuses with absent/hypoplastic nasal bone in second-trimester using chromosomal microarray analysis

BACKGROUND

Pathogenic copy number variants (pCNVs) are associated with fetal ultrasound anomalies, which can be efficiently identified through chromosomal microarray analysis (CMA). The primary objective of the present study was to enhance understanding of the genotype-phenotype correlation in fetuses exhibiting absent or hypoplastic nasal bones using CMA.

METHODS

Enrolled in the present study were 94 cases of fetuses with absent/hypoplastic nasal bone, which were divided into an isolated absent/hypoplastic nasal bone group (n = 49) and a non-isolated group (n = 45). All pregnant women enrolled in the study underwent karyotype analysis and CMA to assess chromosomal abnormalities in the fetuses.

RESULTS

Karyotype analysis and CMA detection were successfully performed in all cases. The results of karyotype and CMA indicate the presence of 11 cases of chromosome aneuploidy, with trisomy 21 being the most prevalent among them. A small supernumerary marker chromosome (sSMC) detected by karyotype analysis was further interpreted as a pCNV by CMA. Additionally, CMA detection elicited three cases of pCNVs, despite normal findings in their karyotype analysis results. Among them, one case of Roche translocation was identified to be a UPD in chromosome 15 with a low proportion of trisomy 15. Further, a significant difference in the detection rate of pCNVs was observed between non-isolated and isolated absent/hypoplastic nasal bone (24.44% vs. 8.16%, p < .05).

CONCLUSION

The present study enhances the utility of CMA in diagnosing the etiology of absent or hypoplastic nasal bone in fetuses. Further, isolated cases of absent or hypoplastic nasal bone strongly suggest the presence of chromosomal abnormalities, necessitating genetic evaluation through CMA.

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.

Follow Your Nose: Repeat Nasal Bone Evaluation in First-Trimester Screening for Down Syndrome

OBJECTIVE

Examine whether repeat nasal bone evaluation following an absent/uncertain nasal bone on first-trimester screening (FTS) improves Down syndrome (DS) screening specificity.

METHODS

A retrospective chart review of FTS sonograms in one center from January 2015 to January 2018 was performed. Data was extracted for those with an absent/uncertain nasal bone. Repeat evaluations were offered.

RESULTS

Of 6780 FTS sonograms, 589 (8.7%) had an absent/uncertain nasal bone. Upon repeat exam, 268/376 (71.3%) had a present nasal bone. Compared with Black patients, patients of other ethnicities were more likely to have a present nasal bone on exam 2 (P < .00001). Of 268 patients with a present nasal bone on exam 2, 37 (13.8%) had an abnormal DS risk following exam 1; 34/37 (91.9%) normalized following nasal bone visualization, dropping the screen positive rate to 1.1%.

CONCLUSION

Repeat nasal bone examination is beneficial in refining DS risk assessment and improves the specificity of FTS.

Study on normal reference value of fetal facial profile markers during the first trimester of pregnancy

BACKGROUND

To establish a normal reference value for fetal facial profile markers during the first trimester of pregnancy.

METHODS

We collected the data of 800 pregnant women who were examined during early pregnancy. The range of values of inferior facial angle (IFA), frontal nasal-mental (FNM) angle, frontomaxillary facial (FMF) angle, mandibulomaxillary facial (MMF) angle, fetal profile line (FPL), and maxilla-nasion-mandible (MNM) angle in normal fetuses of 11-13⁺⁶ weeks was measured and correlated. For the 1,000 fetuses that were screened in the early pregnancy period (11-13⁺⁶ weeks), follow-up the normal fetus, observe and measure the above parameters to obtain the normal measurement range. These markers were measured through GE Voluson E8 ultrasound machines by two experienced sonographers.

RESULTS

A total of Images of 800 fetuses were included in the study. The results showed that the average value of fetal nasal bone was 11.9 mm at 11-13⁺⁶ weeks, which increased with the increase of crown-rump length (CRL); the average value of IFA angle was 64.91°, which has no obvious correlation with CRL; the average value of FNM angle was 143.79°, and the FNM angle decreased slightly with the increase of CRL. Both the FMF angle and the MMF angle decreased with the increase of CRL, and the ratio of FMF/MMF was fixed at 0.75; the average value of MNM angle was 9.55°, which had no obvious correlation with CRL; FP line value was "0" in 177 cases, The positive value of 623 cases did not change significantly with the growth of the fetus, and the gap of the mandible of the normal fetus was almost visible.

CONCLUSIONS

This study established a range of normal reference values for facial and facial angles during early pregnancy, providing a reference for prenatal early detection, early diagnosis of fetal micrognathia, and other facial abnormalities.

Chromosomal Microarray Analysis for the Prenatal Diagnosis in Fetuses with Nasal Bone Hypoplasia: A Retrospective Cohort Study

Background

Previous studies have shown a strong correlation between fetal nasal bone hypoplasia and chromosomal anomaly; however, there is little knowledge on the associations of fetal nasal bone hypoplasia with chromosomal microdeletions and microduplications until now. Chromosomal microarray analysis (CMA) is a high-resolution molecular genetic tool that is effective to detect submicroscopic anomalies including chromosomal microdeletions and microduplications that cannot be detected by karyotyping. This study aimed to examine the performance of CMA for the prenatal diagnosis of nasal bone hypoplasia in the second and third trimesters.

Subjects and Methods

A total of 84 pregnant women in the second and third trimesters with fetal nasal bone hypoplasia, as revealed by ultrasound examinations, were enrolled, and all women underwent karyotyping and CMA with the Affymetrix CytoScan 750K GeneChip Platform. The subjects included 32 cases with fetal nasal bone hypoplasia alone and 52 cases with fetal nasal bone hypoplasia combined with other ultrasound abnormalities, and the prevalence of genomic abnormality was compared between these two groups.

Results

Karyotyping detected 21 cases of chromosomal anomaly in the 84 study subjects (21/84, 25%), including trisomy 21 (14 cases), trisomy 18 (3 cases), 46, del (4)(p16) karyotype (2 cases), 47, XYY syndrome (1 case) and 46, XY, del (5) (p15) karyotype (1 case). CMA detected additional four fetuses with pathogenic copy number variations (CNVs) and six fetuses with uncertain clinical significance (VOUS). No significant difference was detected in the prevalence of genomic abnormality in fetuses with nasal bone hypoplasia alone and in combination with other ultrasound abnormalities (13/32 vs 18/52; χ² = 0.31, P > 0.05). The pregnancy was terminated in 21 fetuses detected with chromosomal abnormality and 4 fetuses detected with pathogenic CNVs. Among the other six fetuses detected with VOUS, the parents chose to continue the pregnancy, and the newborns all had normal clinical phenotypes.

Conclusion

In addition to chromosomal abnormalities identified in 21 fetuses by karyotyping, CMA detected additional 10 fetuses with abnormal CNVs (10/84, 11.9%) in the study population. CMA is a promising powerful tool for prenatal diagnosis that may provide valuable data for the accurate assessment of fetal prognosis and the decision of pregnancy continuation during the prenatal clinical counseling.

Is Noninvasive Prenatal Screening Appropriate for Pregnant Women Age 35 or Older In Cases if Isolated Fetal Nasal Bone Abnormalities in The Chinese Han Population?

Background

Ethnic background may affect the prevalence of nasal bone absence and the length of the nasal bone. This study aimed to elucidate the significance of absent or hypoplastic fetal nasal bone in the Chinese Han population and to formulate an optimal management plan for patients age 35 or older in cases of isolated abnormal fetal nasal bone.

Material/Methods

We prospectively assigned pregnant women whose fetuses had nasal bone absence or hypoplasia to separate groups according to their choice for noninvasive prenatal screening (NIPS) between January 1, 2013, and December 31, 2018. Demographic data, ultrasound findings, results of conventional maternal serum screening and NIPS, fetal karyotype, pregnancy outcomes, and expenses associated with prenatal testing were recorded. The incidence and odds ratio of nasal bone abnormality and the sensitivity and specificity of different prenatal genetic screening tests were calculated.

Results

A total of 1946 cases with fetal nasal bone absence or hypoplasia were included. Cases of isolated nasal bone abnormality (1736 cases) were divided into the NIPS group (Gr 1, n=429) and the non-NIPS group (Gr 2, n=1307). Sixty-four cases involved chromosomal abnormality. The sensitivity, specificity, and positive and negative predictive values of NIPS in Gr 1 were 100%, 100%, 100%, and 100%, respectively. The odds ratio of fetal chromosomal abnormalities for isolated fetal nasal bone abnormalities when maternal age was ≥35 was 4.615 (95% CI: 1.592–13.381). The cost-effectiveness ratio of contingent screening (NIPS first) was significantly lower than amniocentesis directly.

Conclusions

The nasal bone provides an important marker for chromosome abnormalities in some populations, but to a lesser extent in the Chinese Han population. NIPS is an excellent first option for follow-up among pregnant women age ≥35 in cases of absent or hypoplastic fetal nasal bone in the first trimester ultrasound scan.

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.

Assessment of the Nasal Bone by 2-Dimensional Ultrasound in 2 Different Planes: Do They Give the Same Results?

OBJECTIVES

Measurement of the nasal bone is an important part of the genetic sonogram. This study aimed to compare nasal bone length measurements taken in 2 different planes and to determine whether there is consistency between the measurements.

METHODS

The nasal bone was measured in 103 fetuses whose mothers were admitted to our clinic for second-trimester ultrasound examinations and who did not have any accompanying diseases. In this prospective study, the gestational ages of fetuses ranged from 19 to 23 weeks. Nasal bones were measured in both coronal and midsagittal planes, and the similarity between the measurements was evaluated. Pearson correlation, Wilcoxon signed rank, and Kruskal-Wallis tests were used to evaluate the results.

RESULTS

The median nasal bone length increased with increasing gestational age in both planes, as expected. There were no statistically significant differences between the fetal nasal bone lengths taken in the midsagittal and coronal planes at 19 to 23 weeks' gestation (P > .05).

CONCLUSIONS

The coronal plane may be used as an alternative to evaluate the nasal bone in the second trimester of pregnancy.

Current landscape of prenatal genetic screening and testing

Pregnant patients should be offered the option of prenatal genetic screening and diagnostic testing. The type of screening and testing offered to a patient may depend on various factors including but not limited to age, family history, fetal findings, exposures, and patient preferences. Prenatal screening is available for a variety of genetic conditions including aneuploidy, congenital abnormalities, and carrier status. Diagnostic testing options include karyotype, prenatal microarray, as well as next-generation sequencing. The various options differ in methodology, accuracy, timing and indication for testing, and information they provide. Given that the technologies related to prenatal testing are rapidly evolving and improving, the array of available screening and testing modalities are increasing. This article reviews the current offerings in prenatal screening and diagnosis.

Down's syndrome screening at 11-14 weeks' gestation using prenasal thickness and nasal bone length

PURPOSE

To perform a multicenter prospective study of ultrasound prenasal thickness (PT), and nasal bone length (NBL) measurement at 11-14 weeks' gestation.

METHODS

Ultrasound PT and NBL determination was performed in 504 normal fetuses and 17 fetuses with Down's syndrome (DS). Measurements were made from mid-sagittal 2D images acquired using a standardized technique during nuchal translucency (NT) examination. PT and NBL values were expressed in multiples of the gestation-specific normal median (MoM) and as the PT/NBL ratio. Information on PT and NBL MoMs was also combined using logistic regression. Results were classified as positive according to whether they were greater than the normal 95th centile for PT, PT/NBL and the DS risk from logistic regression equation or below the 5th centile for NBL.

RESULTS

The median value in DS cases and unaffected controls were: PT 1.26 and 0.996 MoM; and NBL 0.596 and 0.993 MoM. The proportion of DS fetuses with positive results was 41% for PT, 65% for NBL, and 82% for both the PT/NBL ratio and DS risk from the logistic regression equation. PT/NBL levels did not vary according to gestational age.

CONCLUSION

The PT/NBL ratio is a valuable first trimester DS screening marker that can be easily determined concomitant with the NT measurement.

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.

Prenatal Diagnosis of Recurrent Distal 1q21.1 Duplication in Three Fetuses With Ultrasound Anomalies

Background: The phenotype of duplication of 1q21.1 region is variable, ranging from macrocephaly, autism spectrum disorder, congenital anomalies, to a normal phenotype. Few cases have been reported in the literature regarding prenatal diagnosis of 1q21.1 duplication syndrome. The current study presents prenatal diagnosis of 1q21.1 duplication syndrome in three fetuses with ultrasound anomalies. Case presentation: Three fetuses from three unrelated families were included in the study. The prenatal routine ultrasound examination showed nasal bone loss in Fetus 1 and Fetus 3, as well as duodenal atresia in Fetus 2. Chromosomal microarray analysis was performed to provide genetic analysis of amniotic fluid and parental blood samples. The CMA results revealed two de novo duplications of 1.34 and 2.69 Mb at distal 1q21.1 region in two fetuses with absent nasal bone, as well as a maternal inherited 1.35-Mb duplication at distal 1q21.1 in one fetus with duodenal atresia. Conclusions: The phenotype of 1q21.1 duplication syndrome in prenatal diagnosis is variable. The fetuses with nasal bone loss or duodenal atresia may be related to 1q21.1 duplication and chromosomal microarray analysis should be performed.

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.

Ultrasound screening: Status of markers and efficacy of screening for structural abnormalities

Aneuploidy is a major cause of perinatal morbidity and mortality and can have a significant impact on expecting parents and their families. With early screening and diagnosis it is important to be able to educate parents regarding the potential impact of the diagnosis. This knowledge allows parents the opportunity to consider management options early in the pregnancy, permitting more time to mentally and emotionally prepare both for the course of the pregnancy, and after the birth of the child should the pregnancy continue. Prenatal screening provides pregnant women a non-invasive risk assessment for the most common aneuploidies. Those who are considered "high-risk" then have the option for additional diagnostic (invasive) testing. Prior to the 1980s, prenatal screening consisted of risk assessment through maternal age; however, with the advent of maternal serum biochemical analysis and ultrasound, the field of prenatal screening developed significantly. As biochemical and sonographic advances continued into the 1990s, the emphasis shifted to risk assessment in the first trimester, with the combination of maternal serum analytes and sonographic evaluation of the nuchal translucency.(1) Within the last decade, the introduction of non-invasive screening (NIPT/S) has shown great impact on the expansion and evolving practice of prenatal screening. Although in many places the standard for prenatal testing continues to include maternal serum analytes and sonographic evaluation, the role of each marker alone and in combination remains important. In the era of increasingly available screening tests, especially with NIPT/(NIPS), this article attempts to review the current role of ultrasound in prenatal care and elucidate the role of ultrasound markers in prenatal screening.

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.

Fetal Nasal Bone Status In Iranian Women Undergoing First-Trimester Screening For Trisomy 21: A Review and an Observational Study

Background:

Failed visualization of the fetal nasal bone (NB) by ultrasound at 11 - 14 weeks of gestation is strongly associated with chromosomal abnormalities. Meanwhile, the incidence of the absent fetal NB in normal fetuses in the first trimester in mothers of different ethnic origins differs significantly. It is, therefore, important to assess ethnic variations in the first-trimester visualization of the fetal NB before introducing this marker into routine screening programs for aneuploidy.

Objectives:

The objectives of this study were to determine the NB length and the prevalence of the NB absence as well as calculating the likelihood ratio (LR) for the absence of the NB in normal fetuses of Iranian women undergoing first-trimester screening for trisomy 21.

Patients and Methods:

In 767 normal fetuses, the fetal profile was examined by ultrasound for the absence/presence of the NB. The NB length was also measured, and the LR for the NB absence was also determined.

Results:

The NB was absent in 2/767 (0.26%) of the fetuses. The mean length of the NB was 3.6 ± 0.69 mm for the fetuses of 11 - 14 weeks gestational age. The LR value of the absent NB was equal to 250 in the normal fetuses of the Iranian population living in the North-West provinces.

Conclusion:

The low prevalence of the NB absence in normal fetuses in the present study is compatible with the larger size of the NB in Iranian people compared to other communities. Meanwhile, the reference range of the NB length in normal Iranian fetuses was established so that basic data could be recorded for further studies regarding the absence or presence of the NB in screening for chromosomal abnormalities (Down syndrome) within the Iranian population.

Prenasal thickness to nasal bone length ratio in normal and trisomy 21 fetuses at 11-14 weeks of gestation

OBJECTIVE

To show the feasibility and to create a reference range for prenasal thickness (PT) and for the PT to nasal bone length (NBL) ratio in normal fetuses at 11-14 gestational weeks and to compare the findings to fetuses with trisomy 21.

METHOD

PT, NBL and PT/NBL ratio were measured retrospectively in stored two-dimensional images of 1155 normal fetuses and 44 fetuses with trisomy 21. Mid-sagittal images were acquired at first trimester ultrasound examinations and were selected from our digital database.

RESULTS

The PT increased with CRL from 1.0 mm at 45-mm CRL to 1.6 mm at 84-mm CRL. The mean PT/NBL ratio was 0.6 and was not altered by CRL. The mean PT/NBL ratio in fetuses with trisomy 21 was significantly higher than in normal fetuses (p < 0.0001). For a cut-off value of 0.8 the PT/NBL yielded a sensitivity of 86.4% and a specificity of 98.4% for trisomy 21.

CONCLUSION

The assessment of PT between 11 and 14 gestational weeks is feasible with high intraclass correlation. The PT to NBL ratio seems to be a promising marker for trisomy 21 in the first trimester and was superior to the isolated contribution of NBL and PT measurements.

Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging (MRI) in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and MRI in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost effectiveness, and to identify research opportunities. This article is the executive summary of the workshop.

Advances in ultrasound imaging for congenital malformations during early gestation

BACKGROUND

With refinement in ultrasound technology, detection of fetal structural abnormalities has improved and there have been detailed reports of the natural history and expected outcomes for many anomalies. The ability to either reassure a high-risk woman with normal intrauterine images or offer comprehensive counseling and offer options in cases of strongly suspected lethal or major malformations has shifted prenatal diagnoses to the earliest possible gestational age.

METHODS

When indicated, scans in early gestation are valuable in accurate gestational dating. Stricter sonographic criteria for early nonviability guard against unnecessary intervention. Most birth defects are without known risk factors, and detection of certain malformations is possible in the late first trimester.

RESULTS

The best time for a standard complete fetal and placental scan is 18 to 20 weeks. In addition, certain soft anatomic markers provide clues to chromosomal aneuploidy risk. Maternal obesity and multifetal pregnancies are now more common and further limit early gestation visibility.

CONCLUSION

Other advanced imaging techniques during early gestation in select cases of suspected malformations include fetal echocardiography and magnetic resonance imaging.

[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.

First Trimester Ultrasound in Prenatal Diagnosis-Part of the Turning Pyramid of Prenatal Care

First-trimester sonographic assessment of the risk of chromosomal abnormalities is routinely performed throughout the world, primarily by measuring fetal nuchal translucency thickness between 11–13 weeks’ gestation, combined with assessment of serum markers. The development of high-frequency transvaginal transducers has led to improved ultrasound resolution and better visualization of fetal anatomy during the first-trimester. Continuous improvement in ultrasound technology allows a thorough detailed assessment of fetal anatomy at the time of the nuchal translucency study. Using transabdominal or transvaginal sonography, or a combination of both approaches, it is now possible to diagnose a wide range of fetal anomalies during the first trimester. Multiple studies reported early diagnosis of major fetal anomalies after demonstrating the association of increased nuchal translucency thickness with structural defect in chromosomally normal and abnormal fetuses. Normal sonographic findings provide reassurance for women at high risk while detection of fetal malformation during the first trimester enables discussion and decisions about possible treatments and interventions, including termination of pregnancy, during an early stage of pregnancy.

Nasal bone length: prenasal thickness ratio: a strong 2D ultrasound marker for Down syndrome

Objectives

To evaluate the feasibility of incorporating two-dimensional ultrasound measurements of nasal bone length (NBL) and prenasal thickness (PT) into the second-trimester anomaly scan and to determine whether the NBL : PT ratio could help in differentiating euploid and Down syndrome fetuses.

Method

Two-dimensional measurements of NBL and PT were obtained from the midsagittal plane of the fetal head at 14–28 weeks of gestation in a Caucasian population at risk for aneuploidy. The screening performances of NBL, PT, and the ratios NBL : PT and PT : NBL were analyzed in euploid (n = 1330) and Down syndrome (n = 33) fetuses.

Results

Nasal bone length and PT alone showed strong correlations with Down syndrome (sensitivity: 76% at 1.88% and 2.35% false positive rate, respectively). However, the NBL : PT ratio showed an even stronger correlation with Down syndrome (false positive rate: 0.9%, sensitivity: 97%). The mean NBL : PT ratio showed a gradual increase from 1.48 to 1.79 (a 21.2% increase) between 14 and 28 weeks of gestation.

Conclusion

Two-dimensional ultrasound measurements of NBL and PT, particularly the NBL : PT ratio, are highly sensitive markers for Down syndrome fetuses. © 2014 The Authors. Prenatal Diagnosis published by John Wiley & Sons, Ltd.

Fetal imaging: Executive summary of a Joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and magnetic resonance imaging in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost-effectiveness and to identify research opportunities. This article is the executive summary of the workshop.

Fetal imaging: executive summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, American Institute of Ultrasound in Medicine, American College of Obstetricians and Gynecologists, American College of Radiology, Society for Pediatric Radiology, and Society of Radiologists in Ultrasound Fetal Imaging Workshop

Given that practice variation exists in the frequency and performance of ultrasound and magnetic resonance imaging (MRI) in pregnancy, the Eunice Kennedy Shriver National Institute of Child Health and Human Development hosted a workshop to address indications for ultrasound and MRI in pregnancy, to discuss when and how often these studies should be performed, to consider recommendations for optimizing yield and cost effectiveness, and to identify research opportunities. This article is the executive summary of the workshop.

First-trimester assessment of nasal bone using retronasal triangle view: a prospective study

OBJECTIVE

To examine the feasibility and accuracy of fetal nasal bone (NB) assessment in the retronasal triangle (RNT) view for aneuploidy screening in the first trimester of pregnancy.

METHODS

Consecutive women with singleton pregnancies undergoing sonographic screening at 11-13 weeks' gestation were prospectively evaluated. In all cases, assessment of the NB by using the RNT view was attempted and classified as present (if one or both of the NBs were clearly seen) or absent/hypoplastic (if the NB was not visualized or if it was small and less echogenic than the surrounding bones). The detection rate of fetal karyotypic abnormalities by the assessment of the NB in the RNT view was calculated.

RESULTS

In total, 1977 women were scanned. The RNT was successfully examined in 1970 fetuses (99.6%). Fetal outcome was available in 1767 (89.7%) of evaluated cases, and of these, 39 (2.2%) cases of aneuploidy were documented (trisomy 21, n=17; trisomy 18, n=8; trisomy 13, n=5; Turner syndrome, n=5; and triploidy, n=4). The prevalence of absent/hypoplastic NB was 12/1728 (0.7%) in chromosomally normal fetuses and 12/17 (70.6%) in trisomy 21 fetuses. Sensitivity, specificity and positive and negative predictive values of absent/hypoplastic NB for trisomy 21 were 70.6%, 99.3%, 50.0% and 99.7%, respectively. The positive and negative likelihood ratios of NB assessment were 101 (95% CI, 53-193) and 0.3 (95% CI, 0.14-0.62), respectively.

CONCLUSIONS

The RNT view is a useful technique for assessing the NB during the first trimester of pregnancy. With this new approach, performance of absent/hypoplastic NB as a marker of aneuploidy, mainly trisomy 21, appears to be similar to that previously reported by using the mid-sagittal plane.

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.

Detection of structural abnormalities in the first trimester using ultrasound

During the past 25 years, embryonic and early fetal ultrasound and diagnosis have increasingly gained attention in pregnancy care. Modern high-frequency ultrasound transducers make it possible to obtain detailed images of the early conceptus and its organs, and thus move part of the anatomy and anomaly scan from the second to the first trimester. Today, detection of embryonic and fetal structural abnormalities in the first trimester has frequently been reported. One has to distinguish between diagnosis during the early period until about 10 weeks when the embryo or early fetus is small and transvaginal ultrasound is applied, and diagnosis during the late period at the nuchal translucency screening, usually carried out using transabdominal ultrasound. Early first-trimester abnormalities are often diagnosed by chance on clinical indications, whereas late first-trimester diagnoses are the result of systematic screening using ultrasound markers.

Absent fetal nasal bone: what does it mean for the euploid fetus?

OBJECTIVES

Our purpose was to review the outcomes of singleton pregnancies in which an absent nasal bone was noted on first- or second-trimester sonography and aneuploidy was not present.

METHODS

We identified singleton pregnancies from 2005 to 2011 in which an absent nasal bone was noted on sonography, aneuploidy was excluded, and newborn examinations were available for review. Sonographic reports were reviewed for anomalies, growth, and amniotic fluid volume. Newborn records were reviewed for physical examinations, complications, and radiologic or genetic tests.

RESULTS

We identified 142 fetuses with a sonographic appearance of an absent nasal bone. We excluded 52 cases with aneuploidy and 33 in which newborn examination information was unavailable. Fifty-seven cases met inclusion criteria. For 3 euploid fetuses with an absent nasal bone on sonography, the presence of additional anomalies on second-trimester sonography ultimately signaled an adverse outcome: the presence of multiple congenital anomalies, a microdeletion syndrome, and a specific genetic diagnosis.

CONCLUSIONS

All cases with adverse outcomes had additional prenatal sonographic findings. For the remainder, normal newborn examination findings provide some reassurance, especially in the setting of otherwise normal second-trimester sonographic findings. A microarray as a test for microdeletion and duplication syndromes in this situation could be considered.

Follow-up of sonographically detected soft markers for fetal aneuploidy

Sonographic soft markers of fetal Down syndrome were first reported in the 1980s. With improvements in aneuploidy screening, detection rates of 90% and higher are possible, and such screening is offered to women of all ages. The utility of sonographic detection and reporting of soft markers, particularly to women at low risk of fetal aneuploidy, is controversial. Some soft markers have no additional significance beyond an association with aneuploidy, while some potentially indicate other pathology, and therefore require sonographic follow-up or other evaluation. The definitions of soft markers vary among reported series, and any practice using such markers to adjust the risk of aneuploidy should carefully determine the most appropriate definitions as well as likelihood ratios and how to apply these in practice.

Predictive role of prenasal thickness and nasal bone for Down syndrome in the second trimester

OBJECTIVE

To assess the efficacy of prenasal thickness (PNT) and nasal bone (NB) for prediction of Down syndrome (DS) fetuses in the second trimester ultrasound examination.

STUDY DESIGN

PNT was measured from stored two-dimensional fetal profile images taken at 15-23 weeks in 242 fetuses with normal karyotype (Group 1) and 24 fetuses with DS (Group 2). It was measured as the shortest distance from the anterior edge of the lowest part of the frontal bone to the skin. The efficacy of PNT, NB, PNT/NB and biparietal diameter (BPD)/NB was evaluated for prediction of DS.

RESULTS

PNT values increased with gestational age in normal fetuses. PNT measurement was ≥95th percentile in 54.2% (13/24) of the DS cases and 2.9% of the normal cases. Receiver operator curve analysis showed that PNT/NB ratio had the best area under the curve with a detection rate of 80% for a false positive rate of 5% at a cut-off value of 0.76.

CONCLUSIONS

PNT is increased in fetuses with DS as compared to normal fetuses. PNT/NB≥0.76 in the second trimester is a better predictor of DS than the use of PNT or NB alone.

Reliability of fetal nasal bone length measurement at 11-14 weeks of gestation

Background

Nasal bone assessment has been incorporated into Down syndrome screening in first trimester. Several studies have established the normal reference values for fetal nasal bone length in the first trimester, which were found to be varied by population. However, the study on reliability of nasal bone length measurement was limited with contradictory results. This study aimed to investigate the reliability of fetal nasal bone length measurement at 11–14 weeks of gestation in the Thai population.

Methods

A total of 111 pregnant women at 11–14 weeks of gestation attending for the routine first-trimester ultrasound examination were recruited. Each case was measured separately by two examiners. Examiner 1 performed the first measurement in all cases; any of the other 5 examiners consecutively performed the second measurement. Three independent measurements were performed by each examiner and they were blinded to the results of the others. Intraobserver and interobserver variabilities were evaluated with the intraclass correlation coefficient (ICC).

Results

Nasal bone measurement was successfully performed in 106/111 cases (95.5%) by at least one examiner; 89 cases were performed by two examiners. The intraobserver variability was excellent for all examiners (ICC, 0.840-0.939). The interobserver variability between different pairs of examiners varied from moderate to excellent (ICC, 0.467-0.962). The interobserver variability between examiner 1 and any other examiner was good (ICC, 0.749). The Bland-Altman plot of the interobserver differences of nasal bone length measurements between examiner 1 and any other examiner showed good agreement.

Conclusions

The reliability of the fetal nasal bone length measurement at 11–14 weeks of gestation was good. The nasal bone length measurement was reproducible. Ethnicity has an effect on fetal nasal bone length, but reliability of nasal bone length measurement is critical to accuracy of screening and should be audited on an ongoing basis.

Nasal bone assessment in fetuses with trisomy 21 at 16-24 weeks of gestation by three-dimensional ultrasound

OBJECTIVE

This study aims to investigate the length and shape of the nasal bones in fetuses with trisomy 21 at 16-24 weeks' gestation.

METHOD

We acquired three-dimensional volumes of the fetal profile from 41 fetuses with trisomy 21. The multiplanar mode was used to measure nasal bone length in the exact midsagittal plane and in parasagittal and oblique views of the fetal face and to examine the nasal bones in the coronal plane.

RESULTS

There was bilateral absence of the nasal bones in 11 (26.8%) cases and unilateral absence in one (2.4%). In 29 (70.7%) cases with present nasal bones, there was progressive over-estimation of nasal bone length when measured in parasagittal and oblique views compared to measurements taken in the exact midsagittal plane. In the coronal plane, in 18 of 29 (62.1%) fetuses with trisomy 21, the nasal bones were divergent, whereas in 131 of 135 (97.0%) euploid fetuses, the bones were entirely fused in the midline.

CONCLUSION

Parasagittal and oblique scanning planes may produce over-estimation of nasal bone length in trisomy 21 fetuses because they often have divergent nasal bones. Consequently, it is essential that measurement of nasal bone length is carried out in the exact midsagittal plane of the face.

Validation of first trimester screening for trisomy 21 in Singapore with reference to performance of nasal bone

INTRODUCTION

The aim of this study is to describe the performance of first trimester screening (FTS) for trisomy 21 using maternal age, serum biochemistry and fetal nuchal translucency (NT) in a single center and to evaluate the effect of nasal bone on screening performance.

MATERIAL AND METHODS

In 12,585 singleton pregnancies, the NT and nasal bone were examined. The majority of these mothers also had their serum biochemical markers analyzed. Risk was computed using different combinations of maternal age, biochemistry, NT and nasal bone. Down syndrome cases were confirmed by karyotyping.

RESULTS

There were 12,519 normal pregnancies, 31 with trisomy 21 and 35 with other chromosomal abnormalities. Without considering the nasal bone, the combined FTS detected 87.1% of trisomy 21 fetuses (false positive rate 5.1%), using 1:300 as the risk threshold, and this was further improved to 96.8% with the policy that classifies all fetuses with an absent nasal bone as high risk. Subgroup analysis showed that the detection rate would be 90.9%, with a false positive rate of 3.7%, if nasal bone was incorporated in the risk algorithm, compared to 81.8% and a false positive rate of 5.4% if it was not used.

DISCUSSION

FTS is very effective in early detection of trisomy 21 in Singapore. The nasal bone is a useful marker that can substantially improve the screening performance.

Phenotypic variability in fetuses with down syndrome: a case-control pathological evaluation

OBJECTIVES

Evaluation of morphological and morphometric characteristics of fetuses with Down syndrome based on a detailed postmortem examination and comparison of these fetuses with a control group of fetuses with normal karyotype to improve the prenatal knowledge of Down syndrome characteristics.

MATERIAL AND METHODS

A case-control study was undertaken in a tertiary referral hospital. The Down syndrome fetuses (50) were compared with chromosomally normal fetuses (47) matched for gestational age. Biometric and morphological parameters were compared.

RESULTS

The biometry of fetuses with Down syndrome differs from control fetuses only in the occipitofrontal diameter and in the nasal bone length. There were craniofacial anomalies in 96% of fetuses with Down syndrome and in 51% of fetuses with normal karyotype. With the exception of small ears, all craniofacial features analyzed were significantly different between Down syndrome fetuses and control fetuses. All extremity features of fetuses with Down syndrome were significantly different from fetuses without Down syndrome. There were 31 fetuses with Down syndrome (62%) with 55 internal anomalies. Nineteen fetuses (38.8%) showed 27 cardiac anomalies. Six fetuses had more than one anomaly. There were 18 fetuses (36%) with 28 noncardiac anomalies.

DISCUSSION

The importance of studying the morphological characteristics of fetuses with Down syndrome is the contribution to a better knowledge of fetal characteristics and probably to optimize prenatal diagnosis.

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.

First-trimester screening: dealing with the fall-out

The articles collected together in this issue describe first-trimester screening for a variety of complications. With the advance of both technology and research, early pregnancy screening is becoming ever more sophisticated and complex. While there are clear benefits to most women receiving early reassurance that their baby is developing as expected, there is no evidence to suggest that an earlier prenatal diagnosis has less long-term emotional impact than at later gestations. The poignancy of ultrasound images for many parents means that it can be especially difficult to manage the anxiety when an ultrasound marker is highlighted as potential cause for concern. They can then face a journey of anxiety-laden uncertainty, which can extend through much of the pregnancy, and even beyond. Professionals involved in screening need to recognise and acknowledge such adverse side-effects and develop the skills necessary to help parents understand and cope with the uncertainties inherent in the process.

Assessment of the ductus venosus, tricuspid blood flow and the nasal bone in second-trimester screening for trisomy 21

OBJECTIVE

To examine the prevalence of reversed a-wave in the ductus venosus, tricuspid regurgitation and absent nasal bone, in a second-trimester population undergoing amniocentesis, after exclusion of major fetal defects and to estimate the performance in screening for trisomy 21 based on maternal age and these markers in a general population.

METHODS

This was a retrospective study involving pregnancies undergoing amniocentesis due to increased risk for trisomy 21, mainly because of advanced maternal age. Before the invasive procedure, an ultrasound examination was carried out to exclude major fetal defects and to examine the ductus venosus, tricuspid blood flow and the presence of the fetal nasal bone. Modeling techniques were used based on 20 000 euploid pregnancies and 20 000 pregnancies with trisomy 21 to assess the screening performance in a general population.

RESULTS

The study population consisted of 3613 euploid pregnancies and 35 cases with trisomy 21. In the euploid group, reversed flow in the ductus venosus, tricuspid regurgitation and an absent nasal bone was observed in 1.7%, 1.5% and 0.1% of cases, respectively. In the trisomic group, these markers were found in 14.3%, 11.4% and 14.3% of cases, respectively. For a 5% false-positive rate, the detection rate in screening for trisomy 21, based on maternal age and either ductus venosus, tricuspid blood flow or nasal bone would be 33.8%, 32.4% or 31.4%, respectively. Screening by maternal age alone would detect 29.0% of the fetuses with trisomy 21. Receiver-operating characteristics curve analysis showed a slight but significant improvement in screening performance for trisomy 21 based on the inclusion of these markers.

CONCLUSION

Second-trimester ultrasound screening for trisomy 21 based on maternal age with additional assessment of the ductus venosus, tricuspid blood flow and the fetal nasal bone in otherwise normal-appearing fetuses is only marginally better than is screening by maternal age alone.

Evaluation of fetal nasofrontal angle in the second trimester in normal pregnancies

PURPOSE

The nasal bone is one of the important fetal structures to be radiologically evaluated in the first and second trimesters. In this study, we aimed to evaluate the nasal root and to determine the normal range of the naso-frontal angle, which may potentially be used as a predictive or diagnostic parameter in the diagnosis of the above-mentioned syndromes or other congenital abnormalities with associated nasal features using obstetric ultrasonography in normal fetuses.

METHODS

We evaluated the naso-frontal angle using transabdominal ultrasonography in 195 healthy fetuses between the 18(th) and 21(st) weeks of gestation. The measurements were performed with the fetal neck in mild flexion and three echogenic lines (nasal end, skin on the nasal bone, nasal bone) visualized.

RESULTS

The minimum, maximum and mean naso-frontal angle values were 110°, 143° and 128°, respectively, between the 18(th) and 21(st) weeks of gestation. Linear regression analysis showed no association between NFA and gestational week (Beta = 0.020 p = 0.786).

CONCLUSIONS

The normal range of NFA between the 18(th) and 21(st) weeks of gestation was determined in this study. The association between NFA measurements and various congenital anomalies or fetal outcomes remains to be investigated.

Additional first-trimester ultrasound markers

The first trimester (11-13 +6 weeks) ultrasound examination is useful for several reasons: determination of an accurate date of confinement, diagnostic purposes, and screening for fetal defects. Nuchal translucency measurement combined with maternal serum markers (free b-human chorionic gonadotropin and pregnancy-associated plasma protein A) is the mainstay of first-trimester screening for chromosomal defects. However, over the past decade additional ultrasound markers have been developed that improve the performance of this type of screening. The novel markers include evaluation of the nasal bone, fronto-maxillary angle measurement, and Doppler evaluations of the blood flow across the tricuspid valve and in the ductus venosus.

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.

Real-time three-dimensional ultrasound with Live xPlane imaging assists first-trimester acquisition of a true midsagittal section

OBJECTIVE

To determine whether real-time three-dimensional (3D) ultrasound with Live xPlane imaging, which enables the simultaneous display of two real-time high-quality image planes, can assist both operators certified by The Fetal Medicine Foundation (FMF) and non-FMF-certified operators in acquiring a true midsagittal plane in the first trimester.

METHODS

Eight operators, four of them FMF certified (FMF group) and the other four not (non-FMF group), were asked to acquire a fetal image that they believed to represent the true midsagittal plane using real-time 3D ultrasound with Live xPlane imaging as guidance. Each operator was asked to obtain such an image five times from each of five patients. A total of 200 images from 40 patients were obtained and stored for subsequent analysis. All pregnancies were between 11 + 0 and 13 + 6 weeks of gestation. The angle between the falx cerebri and vertical axis (angle of deviation) was then measured by a single operator. A true midsagittal section was defined as an angle of deviation equal to 0 degrees. The angle of deviation and the time taken to acquire each image were compared between FMF and non-FMF groups.

RESULTS

The median angle of deviation for each operator ranged from 1.2 degrees to 3.4 degrees. There was no significant difference in this angle between those who were FMF certified and those who were not (2.0 degrees vs. 2.2 degrees, P = 0.463). The interquartile range of the angle of deviation was also similar between the FMF- and non-FMF-certified operators. Although the time taken for image acquisition was longer among the non-FMF-certified operators (median, 45.5 s vs. 32.0 s), this difference did not reach statistical significance (P = 0.107).

CONCLUSION

Live xPlane imaging can provide a tool to assist the acquisition of a true midsagittal plane and to determine how true a 'midsagittal' plane really is.

Frontomaxillary facial angle at 11 + 0 to 13 + 6 weeks in Chinese population

OBJECTIVES

To establish the normal range of frontomaxillary facial (FMF) angle in the first trimester in a Chinese population.

METHODS

In a prospective study from March 2007 to June 2007, three-dimensional (3D) volumes of the fetal profile in the mid-sagittal plane were recorded from 129 Chinese pregnant women who were screened for trisomy 21 by the combination of fetal nuchal translucency (NT) thickness, maternal serum free β-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11 to 13 + 6 weeks. 3D volumes were examined using multiplanar techniques. The FMF angle of each case was measured. The relationship between the measured FMF angle with the other parameter was also examined.

RESULTS

The mean FMF angle decreased from 86.8 degree for a crown-rump length (CRL) of 45 mm to 76.0 degree for a CRL of 84 mm (FMF angle = 99.49 - 0.28 x CRL, r=0.377, p<0.0001). There was no significant association between the FMF angle with serum PAPP-A or β-hCG. The mean (SD) difference between FMF angle derived from Chinese formula and that from the published Caucasian equation was 1.47 (0.61) (95% CI 1.37-1.58) (p<0.0001).

CONCLUSIONS

In the first trimester, the FMF angle decreases with fetal CRL. There was similarity in the normal value of FMF angle between the Chinese and Caucasian populations.