Facial profile markers in second- and third-trimester fetuses with trisomy 18

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.

Ultrasonographic study of fetal facial profile markers during the first trimester

Background

To establish reference ranges of fetal facial profile markers and study their correlations with crown-rump length (CRL) during the first trimester (11 ~ 13^+ 6 weeks’ gestation) in a Chinese population.

Methods

Ultrasonographic images of measuring fetal nuchal translucency (NT) were retrospectively selected randomly in normal fetuses whose parents were both Chinese. The facial markers included inferior facial angle (IFA), maxilla-nasion-mandible (MNM) angle, facial maxillary angle (FMA) and profile line (PL) distance. These markers were measured through ViewPoint 6 software by two experienced sonographers.

Results

Three hundred and eighty fetuses were selected. The ICCs (95 % CI) of intra-operator 1 reproducibility of IFA, MNM angle, FMA, PL distance were 0.944 (0.886 ~ 0.973), 0.804 (0.629 ~ 0.902), 0.834 (0.68 ~ 0.918) and 0.935 (0.868 ~ 0.969), respectively. The ICCs (95 % CI) of intra-operator 2 reproducibility of IFA, MNM angle, FMA, PL distance were 0.931 (0.857 ~ 0.967), 0.809 (0.637 ~ 0.904), 0.786 (0.600 ~ 0.892) and 0.906 (0.813 ~ 0.954), respectively. The ICCs (95 % CI) of inter-operator reproducibility of IFA, MNM angle, FMA, PL distance were 0.885 (0.663 ~ 0.953), 0.829 (0.672 ~ 0.915), 0.77 (0.511 ~ 0.891) and 0.844 (0.68 ~ 0.925), respectively. The average ± SD of IFA, MNM angle, FMA and PL distance were 80.2°±7.25°, 4.17°±1.19°, 75.36°±5.31°, 2.78 ± 0.54 mm, respectively. IFA and PL distance significantly decreased with CRL, while MNM angle and FMA significantly increased with CRL.

Conclusions

It was feasible to measure fetal facial markers during the first trimester. In Chinese population, the reference ranges of IFA, MNM angle, FMA and PL distance were 80.2°±7.25°, 4.17°±1.19°, 75.36°±5.31°, 2.78 ± 0.54 mm, respectively, and the measurements were found to correlate with CRL.

Assessment of the maxilla-mandible-nasion angle in normal and aneuploid foetuses in the first trimester of pregnancy

PURPOSE

This retrospective study aims to determine whether the maxilla-mandible-nasion (MMN) angle can be reliably measured in the first trimester, to describe normal ranges, and to determine if significant changes occur in foetuses with aneuploidies.

METHODS

The MMN angle was measured in stored 2D-ultrasound images of 200 normal fetal profiles between 11⁺⁰ and 13⁺⁶ weeks of gestation. Each image was analyzed by two observers at two independent time points. Bland-Altmann analysis was performed to evaluate the reliability of the measurements. Additionally, the MMN angle was measured on sonograms from 140 aneuploid foetuses.

RESULTS

The mean MMN angle in normal foetuses from 11 to 14 weeks of gestation was 15.4°. Reliability of the measurement was high when repeatedly measured by the same observer (ICC = 0.92 and 0.82) and between two observers (ICC = 0.77 and 0.63). Average MMN values in foetuses with trisomy 21, 13, and Turner syndrome were significantly higher than those measured in normal foetuses. The highest differences were observed in foetuses with trisomy 13. Among those, 62% had an MMN angle above the 95th percentile and 92% above the normal mean.

CONCLUSION

The MMN angle can be reliably measured in early pregnancy and is abnormal in about 60% of foetuses with trisomy 13.

Maxilla-nasion-mandible (MNM) angle: an indicator to assess fetal facial profile in first-trimester of pregnancy

Objective

The aim of this study was to observe whether there existed significant differences in the maxilla–nasion–mandible angle (MNM) between the first- and second-trimester of pregnancy, and to observe its predictive values for trisomy 18.

Methods

Two experienced ultrasonologists used 2D and 3D ultrasound imaging techniques to obtain the facial sagittal sections of fetuses in the first-trimester of pregnancy (crown-rump length 45–84 mm), respectively, so as to measure MNM.

Results

MNM could be measured in 91 % of normal fetuses, and the measurement differences by different operators in different groups were <1.1°; average MNM was 11.0°, and no significant change was observed in different gestational ages (P = 0.15). The average of MNMs in fetuses with trisomy 18 was 16.6°, which were all higher than the 95th percentile of normal measurement data. The sensitivity and specificity of increased MNM on the abnormal detection of trisomy 18 were 54.7 and 97.4 %, respectively.

Conclusions

The feasibility and reproducibility of measuring MNM in early pregnancy were good. MNM had certain suggestive roles for aneusomic chromosomal abnormalities, especially for fetuses with trisomy 18.

Fetal facial profile markers of Down syndrome in the second and third trimesters of pregnancy

OBJECTIVES

To investigate the use of the maxilla-nasion-mandible (MNM) angle and fetal profile (FP) line to assess the degree of midfacial hypoplasia in Down-syndrome fetuses in the second and third trimesters of pregnancy.

METHODS

The MNM angle and FP line were measured retrospectively in stored two-dimensional images or three-dimensional volumes of fetuses with Down syndrome. Data collected from January 2006 to July 2013 were retrieved from the digital databases of participating units. The MNM angle was expressed as a continuous variable (degrees) and the FP line as positive, negative or zero. Measurements were obtained from stored images in the midsagittal plane by two experienced examiners and compared with our previously reported normal ranges for euploid fetuses. A MNM angle below the 5(th) centile of the reference range and a positive or negative FP line were considered as abnormal.

RESULTS

A total of 133 fetuses with Down syndrome were available for analysis, eight of which were subsequently excluded because of inadequate images. The MNM angle was not influenced by gestational age (P = 0.48) and was significantly smaller in Down-syndrome fetuses than in euploid fetuses (mean, 12.90° vs 13.53°, respectively; P = 0.015). The MNM angle was below the 5th centile for euploid fetuses in 16.8% of fetuses with Down syndrome (P < 0.01). In the cohort of Down-syndrome fetuses, a positive FP line was present in 41.6% of cases (with a false-positive rate (FPR) of 6.3%) and was positively correlated with Down syndrome and gestational age (P < 0.01). There was no case with a negative FP line. In cases of Down syndrome, a positive FP line was correlated with a small MNM angle (P < 0.01).

CONCLUSIONS

A small MNM angle and a positive FP line can be regarded as novel markers for Down syndrome. The FP line is an easy marker to measure, has a low FPR, does not require knowledge of normal reference values and has the potential to differentiate between Down syndrome and trisomy 18, as, in the latter, the FP line is often negative.