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

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.

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.

Auditing fetal nasal bone images in the first trimester of pregnancy: results from a peer review program

OBJECTIVE

To establish a structured review process to facilitate the identification of the fetal nasal bone (NB) in the first trimester ultrasound scan to improve the quality images.

METHODS

We conducted a retrospective observational study in fetal NB images obtained during ultrasound exams of singleton pregnancies that underwent first trimester screening (crown-rump length 45-84 mm). When the images were obtained the examiner was not aware of the study. Audit was conducted by an examiner according criteria established by the Fetal Medicine Foundation. Fetal NB images were assessed regarding adequate magnification, mid-sagittal view and transducer held parallel to the direction of the nose. The transvaginal and transabdominal as well as anterior and posterior fetal back groups were compared using χ(2) test.

RESULTS

We considered 874 fetal NB images for auditing. Fetal NB was considered present in 865 images (99%). During the audit process, we identified 72 (8.2%) cases of disagreement between examiner and auditor assessments. Disagreement was higher when image quality was poor (62 cases = 7%). Transvaginal approach performed better in the following criteria: adequate magnification (p < 0.001), midline (p < 0.001) and completely adequate (p < 0.001).

CONCLUSION

A peer reviewed audit program for fetal NB is feasible in a clinical scenario. Image quality appears to play an important role in compliance to image standards audited and in agreement between examiner and auditor.

Reference range for the fetal intracranial translucency measurement between 11 and 14 + 2 weeks of gestation in a Brazilian population

OBJECTIVE

To establish a reference range for the fetal intracranial translucency (IT) measurement between 11 and 14 + 2 weeks in a Brazilian population.

METHODS

A retrospective cross-sectional study was performed with 199 low-risk singleton pregnancies during the first trimester ultrasound exam. The IT (fourth ventricle width) measurement was performed in a mid-sagittal view of fetal profile defined by two echogenic borders - the dorsal part of the brain stem anteriorly and the choroid plexus of the fourth ventricle posteriorly. Polynomial regression was used to obtain the best fit using fetal IT measurements and crown-rump length (CRL). Percentiles 5th, 50th and 95th were determined for each gestational age.

RESULTS

The mean of fetal IT ranged from 1.6 mm at CRL 45 to 2.0 mm at CRL 84 mm. A best fit curve was a first-degree polynomial regression: IT measurement = 1.001 + 0.0124 × CRL (R(2)=0.09).

CONCLUSION

Reference range for the fetal IT measurement between 11 and 14 + 2 weeks of gestation in a Brazilian population was established.

The usefulness of volume NT software in measuring the fetal nasal bone at 11 to 13 + 6 weeks of gestation

OBJECTIVE

The objective of this study is to investigate the reproducibility of 3D ultrasound to measure the fetal nasal bone (NB) at first trimester.

METHODS

A group of singleton viable pregnancies attending the 11 to 13 + 6 weeks aneuploidy screening at the University of Bologna were prospectively selected. For each patient, fetal NB was measured by 2D ultrasound. Subsequently, a 3D ultrasound of the fetal head was acquired, and fetal NB was measured by offline analysis using the volume nuchal translucency software. The correlation between 2D and 3D ultrasounds and the reproducibility of fetal NB measurement at 3D ultrasound were assessed.

RESULTS

Overall, 161 Caucasian women were included in the study. At 3D ultrasound, NB measurement showed an excellent intraobserver [Oper 1, intraclass correlation coefficient (ICC) = 0.98; Oper 2, ICC = 0.921] and interobserver agreement (rc = 0.92). The agreement between 2D and 3D measurements was moderate (rc = 0.77).

CONCLUSIONS

A 3D ultrasound supported by the volume nuchal translucency software may provide reliable measurements of the fetal NB in the first trimester.

Reference range of fetal nasal bone length between 18 and 24 weeks of pregnancy in an unselected Brazilian population: experience from a single service

OBJECTIVE

To determine reference range of fetal nasal bone length (NBL) during the second trimester of pregnancy in a Brazilian population.

METHODS

This was a retrospective cross-sectional study with 2681 normal singleton pregnancies between 18 and 24 weeks of gestation. The NBL was obtained in the mid-sagittal plane of the fetal face profile using the following landmarks: nasal bone, overlying skin and the tip of the nose. The NBL was measured by placing the calipers in the out-to-out position. To assess the correlation between NBL and gestational age (GA), polynomial equations were calculated, with adjustments by coefficient of determination (R(2)).

RESULTS

The mean of NBL ranged from 5.72 ± 0.87 mm at 18-18 + 6 weeks to 7.45 ± 1.23 mm at 24-24+6 weeks of pregnancy. We observed a good correlation between NBL and GA, best represented by a linear equation: NBL = 0.080+0.276*GA (R(2 )= 0.16).

CONCLUSION

We established a reference range of fetal NBL in the second trimester of pregnancy in a Brazilian population.

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.

Craniofacial inclination at 14 to 39 weeks' gestation in normal Korean fetuses

OBJECTIVES

The purpose of this study was to evaluate a normal range for prenatal craniofacial inclination using images of fetal profiles at 14 to 39 weeks' gestation in normal Korean fetuses.

METHODS

We conducted a cross-sectional study of 308 normal fetuses at 14 to 39 weeks' gestation. After the exclusion of images with inadequate quality, the sagittal plane of the sonographic fetal facial profile from 250 normal fetuses was evaluated. The frontomaxillary facial, frontonasal, maxilla-nasion-mandibular, and mandibulomaxillary facial angles were measured and are presented according to gestational age.

RESULTS

The overall mean frontomaxillary facial angle ± SD was 86.0° ± 7.6° between 14 weeks 6 days' and 39 weeks 2 days' gestation without a significant association between the frontomaxillary facial angle and gestational week. The overall mean frontonasal, maxilla-nasion-mandibular, and mandibulomaxillary facial angles were 125.8° ± 7.2°, 4.7° ± 3.3°, and 83.2° ± 8.5° between 14 weeks and 39 weeks 6 days. There was a significant linear correlation between gestational age and the frontonasal angle (r = -0.1534; P = .0187; y = -0.188 × gestational age + 130.7), maxilla-nasion-mandibular angle (r = -0.2773; P < .0001; y = -0.160 × gestational age + 9.0), and mandibulomaxillary facial angle (r = -0.2861; P < .0001; y = -0.432 × gestational age + 94.6).

CONCLUSIONS

We provide preliminary normative data for fetal facial angles related to craniofacial inclination across gestational ages in normal Korean fetuses. These data may be of help not only for the understanding of normal facial growth in utero but also for diagnosis of abnormal fetal facial dimensions.

Ultrasound evaluation of the fetal nasal bone: what is the most appropriate first-trimester cut-off point for aneuploidy screening?

PURPOSE

To establish fetal nasal bone length cut-off points for first trimester aneuploidy screening based on a normal curve of a Brazilian population.

METHODS

The following tests were proposed: presence or absence of the nasal bone (NB); 2.5 and 5.0 NB percentiles relative to the normal curve; and 0.70, 0.75 and 0.80 multiples of the median (MoM) values defined in the receiver operating characteristic (ROC) curve. Nasal Bone tests were based on positive and negative likelihood ratio value detection rates (LR); the confidence interval was 95% in all tests. Cases in which ultrasonographic images of the NB were absent were not taken into account when evaluating the 2.5 and 5.0 percentiles and the 0.70, 0.75 and 0.80 MoM.

RESULTS

The sample consisted of 571 fetuses (10-14 weeks). After exclusions (11) and loss of follow-up (53), the study sample was reduced to 507 patients. There were 23 Down syndrome patients among 41 aneuploid fetuses. The sensitivity of the qualitative NB test (absent vs. present) was 34.1%, and the specificity was 99.1% (+LR 37.89, -LR 0.66). An image of the nasal bone was absent in 52.2% of fetuses with the Down syndrome (+LR 58.00, -LR 0.48).

CONCLUSIONS

The best tool for aneuploidy screening was the qualitative NB test (absent vs. present). Ultrasonography of the NB is a component of aneuploidy screening, and should not be used alone.

Frontomaxillary facial angle measurements in euploid Korean fetuses at 11 weeks' to 13 weeks 6 days' gestation

OBJECTIVE

The purpose of this study was to evaluate the distribution of fetal frontomaxillary facial angles in a euploid Korean population at 11 weeks' to 13 weeks 6 days' gestation.

METHODS

Three-dimensional volumes of the fetal head were obtained from women with low-risk singleton pregnancies at 11 weeks' to 13 weeks 6 days' gestation who consented to this prospective study. Only fetuses with either a normal karyotype confirmed by amniocentesis or no abnormalities after delivery were considered eligible for analysis and were characterized as euploid for the purposes of this study. Women with multiple pregnancies and those who were lost to follow-up and fetuses with abnormal karyotypes or anomalies diagnosed in utero or postnatally were excluded. The frontomaxillary facial angle was measured twice offline by a single examiner. Cases were categorized by crown-rump length (CRL) in 10-mm intervals for analysis of the frontomaxillary facial angle.

RESULTS

Among 375 enrolled cases, 158 were eligible for frontomaxillary facial angle analysis. The overall mean frontomaxillary facial angle ± SD was 88.6° ± 9.7°. The mean frontomaxillary facial angle for fetuses with a CRL of 40 to 49 mm (n = 35) was 93.7°; 50 to 59 mm (n = 53), 92.6°; 60 to 69 mm (n = 36), 85.3°; and 70 to 79 mm (n = 34), 81.0°, showing an inverse relationship between the mean frontomaxillary facial angle and CRL (r = -0.5334; P < .0001). The proportion of cases with frontomaxillary facial angles of 85° or greater was 60.8%, and that of cases with angles of 90° or greater was 37.3%.

CONCLUSIONS

Ethnic differences in frontomaxillary facial angle measurements should be considered when incorporating the frontomaxillary facial angle in fetal aneuploidy screening in the Korean population.