Nasal bone hypoplasia in trisomy 21 at 15-22 weeks' gestation.

OBJECTIVE: To investigate the potential value of ultrasound examination of the fetal profile for present/hypoplastic fetal nasal bone at 15-22 weeks' gestation as a marker for trisomy 21. METHODS: This was an observational ultrasound study in 1046 singleton pregnancies undergoing amniocentesis for fetal karyotyping at 15-22 (median, 17) weeks' gestation. Immediately before amniocentesis the fetal profile was examined to determine if the nasal bone was present or hypoplastic (absent or shorter than 2.5 mm). The incidence of nasal hypoplasia in the trisomy 21 and the chromosomally normal fetuses was determined and the likelihood ratio for trisomy 21 for nasal hypoplasia was calculated. RESULTS: All fetuses were successfully examined for the presence of the nasal bone. The nasal bone was hypoplastic in 21/34 (61.8%) fetuses with trisomy 21, in 12/982 (1.2%) chromosomally normal fetuses and in 1/30 (3.3%) fetuses with other chromosomal defects. In 3/21 (14.3%) trisomy 21 fetuses with nasal hypoplasia there were no other abnormal ultrasound findings. In the chromosomally normal group hypoplastic nasal bone was found in 0.5% of Caucasians and in 8.8% of Afro-Caribbeans. The likelihood ratio for trisomy 21 for hypoplastic nasal bone was 50.5 (95% CI 27.1-92.7) and for present nasal bone it was 0.38 (95% CI 0.24-0.56). CONCLUSION: Nasal bone hypoplasia at the 15-22-week scan is associated with a high risk for trisomy 21 and it is a highly sensitive and specific marker for this chromosomal abnormality.     

Three-dimensional evaluation of mid-facial hypoplasia in fetuses with trisomy 21 at 11 + 0 to 13 + 6 weeks of gestation.

OBJECTIVE: To investigate the mid-facial hypoplasia of fetuses with trisomy 21 at 11 + 0 to 13 + 6 weeks of gestation, by three-dimensional (3D) evaluation of the maxilla and the nasal bones. METHODS: A 3D volume of the fetal head was obtained before fetal karyotyping at 11 + 0 to 13 + 6 (median 12) weeks of gestation in 80 fetuses that were subsequently found to have trisomy 21 and in 862 fetuses subsequently found to be chromosomally normal. The multiplanar mode was used to obtain a sequence of transverse views of the fetal face and to demonstrate the maxilla, the adjacent rami of the mandible and the nasal bones. The maxillary depth, defined as the distance between the alveolus of the maxilla in the midline anteriorly and the midpoint of the line joining the rami posteriorly, was measured. Ossification of the nasal bones was considered to be normal if both bones were more echogenic than the overlying skin. RESULTS: In the chromosomally normal group the maxillary depth increased linearly with crown-rump length (CRL) from 3.1 mm at a CRL of 45 mm to 4.8 mm at a CRL of 84 mm, and in the trisomy 21 fetuses the depth was significantly smaller than normal (mean difference = - 0.3 mm, P < 0.001). There was no significant association between the delta maxillary depth and delta nuchal translucency thickness in either the trisomy 21 or the chromosomally normal fetuses. Impaired ossification of the nasal bones was observed in 3.1% of the chromosomally normal fetuses and in 60.0% of those with trisomy 21. The mean maxillary depth was significantly smaller in fetuses demonstrating impaired ossification than in those with normal ossification of the nasal bones (mean difference = -0.2 mm; 95% CI, -0.3 to -0.1, P = 0.001). CONCLUSIONS: In a high proportion of fetuses with trisomy 21 there is sonographic evidence of mid-facial hypoplasia at 11 + 0 to 13 + 6 weeks of gestation.     

Absent nasal bone at 11-14 weeks of gestation and chromosomal defects.

OBJECTIVE: To examine the association between absence of the nasal bone at the 11-14-week ultrasound scan and chromosomal defects. METHODS: Ultrasound examination was carried out in 3829 fetuses at 11-14 weeks' gestation immediately before fetal karyotyping. At the scan the fetal crown-rump length (CRL) and nuchal translucency (NT) thickness were measured and the fetal profile was examined for the presence or absence of the nasal bone. Maternal characteristics including ethnic origin were also recorded. RESULTS: The fetal profile was successfully examined in 3788 (98.9%) cases. In 3358/3788 cases the fetal karyotype was normal and in 430 it was abnormal. In the chromosomally normal group the incidence of absent nasal bone was related firstly to the ethnic origin of the mother (2.8% for Caucasians, 10.4% for Afro-Caribbeans and 6.8% for Asians), secondly to fetal CRL (4.6% for CRL of 45-54 mm, 3.9% for CRL of 55-64 mm, 1.5% for CRL of 65-74 mm and 1.0% for CRL of 75-84 mm) and thirdly, to NT thickness, (1.8% for NT < 2.5 mm, 3.4% for NT 2.5-3.4 mm, 5.0% for NT 3.5-4.4 mm and 11.8% for NT > or = 4.5 mm. In the chromosomally abnormal group the nasal bone was absent in 161/242 (66.9%) with trisomy 21, in 48/84 (57.1%) with trisomy 18, in 7/22 (31.8%) with trisomy 13, in 3/34 (8.8%) with Turner syndrome and in 4/48 (8.3%) with other defects. CONCLUSION: At the 11-14-week scan the incidence of absent nasal bone is related to the presence or absence of chromosomal defects, CRL, NT thickness and ethnic origin.     

Brachycephaly and frontal lobe hypoplasia in fetuses with trisomy 21 at 11 + 0 to 13 + 6 weeks.

OBJECTIVE: To investigate the incidence of brachycephaly and frontal lobe hypoplasia in fetuses with trisomy 21 at 11 + 0 to 13 + 6 weeks of gestation. METHODS: A three-dimensional (3D) volume of the fetal head was obtained before fetal karyotyping at 11 + 0 to 13 + 6 (median, 12 + 5) weeks of gestation in 100 fetuses that were subsequently found to have trisomy 21 and in 300 fetuses subsequently found to be chromosomally normal. The multiplanar mode was used to obtain a sequence of transverse views of the fetal head and to demonstrate the biparietal and suboccipitobregmatic views. We measured the biparietal diameter (BPD), the occipitofrontal diameter (OFD) and the frontothalamic distance (FTD) between the inner table of the frontal bone and the posterior thalami. RESULTS: In the chromosomally normal group the BPD, OFD and FTD increased linearly with crown-rump length (CRL) from 16.7 mm, 19.0 mm and 12.1 mm at a CRL of 45 mm to 26.7 mm, 31.7 mm and 18.7 mm, respectively, at a CRL of 84 mm. In the trisomy 21 fetuses, compared to normal fetuses, there was shorter BPD (mean difference = -0.63 mm; 95% CI, -0.97 to -0.30 mm, P < 0.0001), OFD (mean difference = -1.41 mm; 95% CI, -1.75 to -1.07 mm, P < 0.0001) and FTD (mean difference = -0.77 mm; 95% CI, -1.02 to -0.54 mm; P < 0.0001) and higher BPD to OFD ratio (mean difference = 0.022; 95% CI, 0.012 to 0.032, P < 0.0001) but no significant difference in the FTD to OFD ratio (mean difference = 0.004; 95% CI, -0.006 to 0.013, P = 0.448). CONCLUSIONS: In fetuses with trisomy 21 at 11 + 0 to 13 + 6 weeks of gestation there is evidence of brachycephaIy but not of frontal lobe hypoplasia.     

Likelihood ratio for trisomy 21 in fetuses with absent nasal bone at the 11-14-week scan.

OBJECTIVE: To update the likelihood ratio for trisomy 21 in fetuses with absent nasal bone at the 11-14-week scan. METHODS: Ultrasound examination of the fetal profile was carried out and the presence or absence of the nasal bone was noted immediately before karyotyping in 5918 fetuses at 11 to 13+6 weeks. Logistic regression analysis was used to examine the effect of maternal ethnic origin and fetal crown-rump length (CRL) and nuchal translucency (NT) on the incidence of absent nasal bone in the chromosomally normal and trisomy 21 fetuses. RESULTS: The fetal profile was successfully examined in 5851 (98.9%) cases. In 5223/5851 cases the fetal karyotype was normal and in 628 cases it was abnormal. In the chromosomally normal group the incidence of absent nasal bone was related first to the ethnic origin of the mother, being 2.2% for Caucasians, 9.0% for Afro-Caribbeans and 5.0% for Asians; second to fetal CRL, being 4.7% for CRL of 45-54 mm, 3.4% for CRL of 55-64 mm, 1.4% for CRL of 65-74 mm and 1% for CRL of 75-84 mm; and third to NT, being 1.6% for NT < or = 95th centile, 2.7% for NT > 95th centile-3.4 mm, 5.4% for NT 3.5-4.4 mm, 6% for NT 4.5-5.4 mm and 15% for NT > or = 5.5 mm. In the chromosomally abnormal group there was absent nasal bone in 229/333 (68.8%) cases with trisomy 21 and in 95/295 (32.2%) cases with other chromosomal defects. Logistic regression analysis demonstrated that in the chromosomally normal fetuses significant independent prediction of the likelihood of absent nasal bone was provided by CRL, NT and Afro-Caribbean ethnic group, and in the trisomy 21 fetuses by CRL and NT. The likelihood ratio for trisomy 21 for absent nasal bone was derived by dividing the likelihood in trisomy 21 by that in normal fetuses. CONCLUSION: At the 11-14-week scan the incidence of absent nasal bone is related to the presence or absence of chromosomal defects, CRL, NT and ethnic origin.     

Single umbilical artery at 11-14 weeks' gestation: relation to chromosomal defects.

OBJECTIVE: To determine the possible association between single umbilical artery (SUA) at 11-14 weeks of gestation and the incidence of chromosomal abnormalities. METHODS: Color flow imaging of the fetal pelvis was used to determine the number of umbilical arteries in 717 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks' gestation. RESULTS: Single umbilical artery (SUA) was diagnosed in 21/634 (3.3%) chromosomally normal fetuses, in 5/44 (11.4%) with trisomy 21, 14/18 (77.8%) with trisomy 18 and 2/21 (9.5%) with other chromosomal defects. In the chromosomally normal group there was no significant difference in median fetal crown-rump length or nuchal translucency (NT) between those with a single and those with two umbilical arteries. In the 42 fetuses with SUA the expected number of cases of trisomy 21, estimated on the basis of maternal age, gestational age and fetal NT, was 4.7, which was not significantly different from the observed 5. The corresponding numbers for trisomy 18 were 2.0 for expected and 14 for observed (Fisher's exact test P = 0.0016). CONCLUSION: A SUA at 11-14 weeks' gestation has a high association with trisomy 18 and other chromosomal defects.     

Likelihood ratios for fetal trisomy 21 based on nasal bone length in the second trimester: how best to define hypoplasia?

OBJECTIVE: To determine the best measure of fetal nasal bone hypoplasia for trisomy 21 risk assessment in the second trimester. METHODS: This was a prospective, observational study performed at a single institution between February 2003 and December 2005. Fetuses with nasal bone length recorded sonographically between 16 and 20.9 weeks and known karyotype were included. Definitions of nasal bone hypoplasia assessed included: non-visualized nasal bone, nasal bone < 10th percentile, nasal bone < 2.5th percentile, biparietal diameter/nasal bone ratio >or= 10 and >or= 11 and nasal bone multiples of the median (MoM) 相似文献   

唐氏综合征胎儿鼻骨的超声研究

目的探讨唐氏综合征(又称21三体综合征)与胎儿鼻骨发育不良的关系。方法产前超声测量901例正常中孕期及570例中孕期唐氏综合征高风险胎儿鼻骨,并对22例引产胎儿的鼻骨行X线检查及大体解剖观察。结果1471例胎儿鼻骨超声检测成功率96%(1413例)。22例唐氏综合征胎儿中,产前超声诊断鼻骨缺失1例,鼻骨发育不良(测值小于2.5mm,包括1例鼻骨缺失)11例。结论唐氏综合征胎儿与鼻骨发育不良有密切关系。     

Ear length in trisomy 21 fetuses at 11-14 weeks of gestation.

OBJECTIVE: To determine the value of measuring fetal ear length at 11-14 weeks of gestation in screening for chromosomal defects. METHODS: The fetal ear length was measured in 450 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks of gestation. RESULTS: The median gestational age was 12 (range, 11-14) weeks. The fetal ear was successfully examined in all cases. The fetal karyotype was normal in 409 cases and abnormal in 41, including 32 cases of trisomy 21. In the chromosomally normal group the fetal ear length increased significantly with crown-rump length from a mean of 3.7 mm at 45 mm to 6.9 mm at 84 mm. In the trisomy 21 fetuses the median ear length was significantly below the normal mean for crown-rump length by 0.45 mm (P = 0.013) but it was below the 5(th) centile of the normal range in only two (6.3%) of the cases. There was no significant association between the delta score of ear length and delta nuchal translucency in either the chromosomally normal (r = - 0.015, P = 0.753) or the trisomy 21 fetuses (r = - 0.014, P = 0.94). CONCLUSIONS: At 11-14 weeks of gestation the ear length in trisomy 21 fetuses is significantly reduced but the degree of deviation from normal is too small for this measurement to be useful in screening for trisomy 21.     

Fetal nasal bone length in euploid and aneuploid fetuses between 11 and 20 weeks' gestation: a prospective study.

OBJECTIVE: To develop normative data for nasal bone length between 11 and 20 weeks' gestation and to assess the utility of nasal bone hypoplasia in the detection of fetal aneuploidy in the second trimester. METHODS: Well-dated, nonanomalous fetuses were examined between 11 and 20.9 weeks' gestation. The nasal bone was assessed and measured, and normative data from 11 to 20 weeks' gestation were determined. The nasal bone lengths in fetuses with confirmed aneuploidy were compared with the normative data. RESULTS: The fetal nasal bone length increased linearly with advancing gestational age. Nomograms including the 10th, 50th, and 90th percentiles were created. Nasal bone hypoplasia was seen in 6 of 6 cases of fetal trisomy in the second trimester. CONCLUSIONS: Nasal bone hypoplasia in the early second trimester identifies a cohort of fetuses at high risk for aneuploidy.     

Femur and humerus length in trisomy 21 fetuses at 11-14 weeks of gestation.

OBJECTIVE: To determine the value of measuring fetal femur and humerus length at 11-14 weeks of gestation in screening for chromosomal defects. METHODS: Femur and humerus lengths were measured using transabdominal ultrasound in 1018 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks of gestation. In the group of chromosomally normal fetuses, regression analysis was used to determine the association between long bone length and crown-rump length (CRL). Femur and humerus lengths in fetuses with trisomy 21 were compared with those of normal fetuses. RESULTS: The median gestation was 12 (range, 11-14) weeks. The karyotype was normal in 920 fetuses and abnormal in 98, including 65 cases of trisomy 21. In the chromosomally normal group the fetal femur and humerus lengths increased significantly with CRL (femur length = - 6.330 + 0.215 x CRL in mm, r = 0.874, P < 0.0001; humerus length = - 6.240 + 0.220 x CRL in mm, r = 0.871, P < 0.0001). In the Bland-Altman plot the mean difference between paired measurements of femur length was 0.21 mm (95% limits of agreement - 0.52 to 0.48 mm) and of humerus length was 0.23 mm (95% limits of agreement - 0.57 to 0.55 mm). In the trisomy 21 fetuses the median femur and humerus lengths were significantly below the appropriate normal mean for CRL by 0.4 and 0.3 mm, respectively (P = 0.002), but they were below the respective 5th centile of the normal range in only six (9.2%) and three (4.6%) of the cases, respectively. CONCLUSION: At 11-14 weeks of gestation the femur and humerus lengths in trisomy 21 fetuses are significantly reduced but the degree of deviation from normal is too small for these measurements to be useful in screening for trisomy 21.     

Fetal heart rate in chromosomally abnormal fetuses.

OBJECTIVES: To determine the effects of chromosomal defects on fetal heart rate at 10-14 weeks of gestation. METHODS: Fetal heart rate at 10-14 weeks of gestation in 1061 chromosomally abnormal fetuses was compared to that from 25,000 normal pregnancies. The chromosomally abnormal group included 554 cases of trisomy 21, 219 cases of trisomy 18, 95 of trisomy 13, 50 of triploidy, 115 of Turner syndrome and 28 of sex chromosome abnormalities other than Turner syndrome. RESULTS: In the normal group, fetal heart rate decreased from a mean value of 170 beats per minute (bpm) at 35 mm of crown-rump length to 155 bpm at 84 mm crown-rump length. In trisomy 21, trisomy 13 and Turner syndrome fetal heart rate was significantly higher, in trisomy 18 and triploidy the heart rate was lower and in other sex chromosome defects it was not significantly different from normal. Fetal heart rate was above the 95th centile of the normal range in 10%, 67% and 52% of fetuses with trisomy 21, trisomy 13 and Turner syndrome, respectively. The fetal heart rate was below the 5th centile in 30% of fetuses with triploidy and 19% of those with trisomy 18. CONCLUSIONS: Trisomy 21, trisomy 13 and Turner syndrome are associated with fetal tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia. Inclusion of fetal heart rate in a first-trimester screening program for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness is unlikely to provide useful improvement in sensitivity.     

Umbilical cord diameter at 11-14 weeks of gestation: relation to chromosomal defects.

OBJECTIVE: To determine the potential value of measuring umbilical cord diameter (UCD) at 11-14 weeks of gestation in screening for chromosomal defects. METHODS: The UCD was measured in 1323 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks of gestation. In the group of chromosomally normal fetuses, regression analysis was used to determine the association between UCD and crown-rump length (CRL). UCD was compared in normal fetuses and those with chromosomal abnormalities. RESULTS: The median gestation was 12 (range, 11-14) weeks. The UCD was successfully measured in all cases. The fetal karyotype was normal in 1150 pregnancies and abnormal in 173, including 97 cases of trisomy 21. In the chromosomally normal group the UCD increased significantly with CRL from a mean of 2.9 mm at a CRL of 45 mm to 4.4 mm at a CRL of 84 mm. The UCD in the group of fetuses with trisomy 21 was significantly smaller than normal. Conversely, there were no significant differences from normal in the UCD of fetuses with other chromosomal abnormalities. CONCLUSION: At 11-14 weeks of gestation the UCD of fetuses with trisomy 21 is significantly smaller than normal but the magnitude of the difference is too small for useful inclusion of this measurement in screening.     

Comparison of fetal nasal bone assessment by ultrasound at 11-14 weeks and by postmortem X-ray in trisomy 21: a prospective observational study.

OBJECTIVE: To compare nasal bone assessment by ultrasound examination at 11-14 weeks' gestation and postmortem X-ray examination in fetuses with trisomy 21. METHODS: Twenty-one fetuses with trisomy 21 which had undergone sonographic examination at 11-14 weeks for measurement of nuchal translucency thickness and assessment of the nasal bones were examined by postmortem X-ray following termination of pregnancy. RESULTS: The nasal bones were absent in 11/21 (52.4%) fetuses on ultrasound examination at 11-14 weeks and in 10/21 (47.6%) fetuses on X-ray examination at 14 to 25 + 5 weeks. Ultrasound and X-ray findings were discordant in 9/21 (42.9%) cases. Eight of 11 (72.7%) fetuses with absent nasal bones on ultrasound examination had a nuchal translucency thickness > 95th centile. CONCLUSION: The high incidence of absent nasal bones in first-trimester fetuses with trisomy 21 is compatible with a developmental delay. Prior to inclusion of nasal bone assessment into risk calculation for trisomy 21, the independence of absence of nasal bones by ultrasound and increased nuchal translucency above the 95th centile at 11-14 weeks should be investigated more extensively.     

Frontomaxillary and mandibulomaxillary facial angles at 11 + 0 to 13 + 6 weeks in fetuses with trisomy 18.

OBJECTIVE: To define the relative position of the maxilla and mandible in fetuses with trisomy 18 at 11 + 0 to 13 + 6 weeks of gestation. METHODS: A three-dimensional (3D) volume of the fetal head was obtained before karyotyping at 11 + 0 to 13 + 6 weeks of gestation in 36 fetuses subsequently found to have trisomy 18, and 200 chromosomally normal fetuses. The frontomaxillary facial (FMF) angle and the mandibulomaxillary facial (MMF) angle were measured in a mid-sagittal view of the fetal face. RESULTS: In the chromosomally normal group both the FMF and MMF angles decreased significantly with crown-rump length (CRL). In the trisomy 18 fetuses the FMF angle was significantly greater and the angle was above the 95(th) centile of the normal range in 21 (58.3%) cases. In contrast, in trisomy 18 fetuses the MMF angle was significantly smaller than that in normal fetuses and the angle was below the 5(th) centile of the normal range in 12 (33.3%) cases. CONCLUSIONS: Trisomy 18 at 11 + 0 to 13 + 6 weeks of gestation is associated with both mid-facial hypoplasia and micrognathia or retrognathia that can be documented by measurement of the FMF angle and MMF angle, respectively.     

Fetal trunk and head volume in chromosomally abnormal fetuses at 11+0 to 13+6 weeks of gestation.

OBJECTIVE: To examine the pattern of growth in chromosomally abnormal fetuses at 11+0 to 13+6 weeks of gestation and compare the trunk and head volume to crown-rump length (CRL) in defining the growth deficit in such fetuses. METHODS: The fetal trunk and head volume was measured using three-dimensional (3D) ultrasound in 140 chromosomally abnormal fetuses at 11+0 to 13+6 (median 12) weeks of gestation, and the values were compared to 500 chromosomally normal fetuses. In each chromosomally abnormal fetus, the observed fetal trunk and head volume was subtracted from the expected mean (delta value) of the chromosomally normal fetuses of the same gestational age, and this difference was expressed as a percentage of the appropriate normal mean. The Mann-Whitney U-test was used to determine the significance of differences between the chromosomally normal and abnormal groups. RESULTS: In trisomy 21 (n=72) and Turner syndrome (n=14) fetuses, compared to chromosomally normal fetuses, the CRL for gestation was similar (P=0.335 and P=0.317, respectively), but the fetal trunk and head volume was about 10-15% lower (P<0.001 and P=0.004, respectively). In trisomy 18 (n=29), trisomy 13 (n=14) and triploidy (n=11), the deficit in volume was about 45% (P<0.001), whereas the deficit in CRL was less than 15% (P<0.001). CONCLUSIONS: In the quantification of the degree of early growth impairment in chromosomally abnormal fetuses, measurement of the fetal trunk and head volume using 3D ultrasound may be better than measurement of CRL.     

Assessment of the gap between the fetal nasal bones at 11 to 13 + 6 weeks of gestation by three-dimensional ultrasound.

OBJECTIVE: To detect the presence of a gap between the fetal nasal bones at 11 to 13 + 6 weeks of gestation and to verify if this gap could lead to the erroneous diagnosis of absent nasal bone. METHODS: Three-dimensional (3D) ultrasound was used to assess the fetal nose in 450 singleton pregnancies, immediately after two-dimensional (2D) evaluation of the nasal bones and screening for chromosomal defects by a combination of maternal age and the measurement of fetal nuchal translucency at 11 to 13 + 6 (median, 12) weeks of gestation. A 3D volume of the fetal face was acquired and then analyzed using the multiplanar mode. A sequence of transverse views was used to confirm the presence or absence of the nasal bones and when they were present any visible gap between them was measured. A perfectly mid-sagittal plane was then examined to determine if the nasal bone was visible or not. RESULTS: In 421/450 (93.6%) cases the nasal bone was present during 2D ultrasound. Using the multiplanar mode of 3D ultrasound, in 83/421 (19.7%) fetuses a gap between the nasal bones could be demonstrated and in 36/83 (43.4%) cases the nasal bone was found to be absent in the perfect mid-sagittal view. In 29/450 (6.4%) cases the nasal bones were absent during the 2D scan. In the 3D assessment there was absence of both bones in 25/29 (86.2%) cases and absence of one of the two bones in 4/29 (13.8%) cases. Chorionic villus sampling demonstrated that the fetal karyotype was normal in 404 and abnormal in 46 cases, including 31 cases of trisomy 21. There was absence of one or both nasal bones in three (0.7%) of the chromosomally normal fetuses, in 19 (61.3%) with trisomy 21 and in seven (46.7%) with other chromosomal defects. CONCLUSIONS: At 11 to 13 + 6 weeks of gestation there is a gap between the nasal bones in about 20% of fetuses, and in about 40% of these cases in the perfect mid-sagittal plane the nasal bone may erroneously be considered to be absent.     

Likelihood ratio for trisomy 21 in fetuses with tricuspid regurgitation at the 11 to 13 + 6-week scan.

OBJECTIVE: To determine the likelihood ratio for trisomy 21 in fetuses with tricuspid regurgitation at the 11 to 13 + 6-week scan. METHODS: Fetal echocardiography was carried out by specialist pediatric cardiologists in 742 singleton pregnancies at 11 to 13 + 6 weeks' gestation and pulsed wave Doppler was used to ascertain the presence or absence of tricuspid regurgitation. To avoid confusion with other adjacent signals, a strict definition of tricuspid regurgitation was used, in that it had to occupy at least half of systole and reach a velocity of over 80 cm/s. The fetal crown-rump length (CRL) and the nuchal translucency (NT) thickness were measured and the presence of any congenital heart abnormality noted. Follow-up of the pregnancy was carried out to determine the presence of chromosomal abnormalities. The likelihood ratio for trisomy 21 in fetuses with and without tricuspid regurgitation was determined. RESULTS: The tricuspid valve was successfully examined in 718 (96.8%) cases. Tricuspid regurgitation was present in 39 (8.5%) of the 458 chromosomally normal fetuses, in 82 (65.1%) of the 126 with trisomy 21, in 44 (53.0%) of the 83 with trisomy 18 or 13, and in 11 (21.6%) of the 51 with other chromosomal defects. The prevalence of tricuspid regurgitation was also associated with fetal CRL, delta NT and the presence of cardiac defects. Logistic regression analysis, irrespective of cardiac defects, demonstrated that in the chromosomally normal fetuses significant independent prediction of the likelihood of tricuspid regurgitation was provided by fetal delta NT (odds ratio (OR), 1.26; 95% CI, 1.34-1.41; P < 0.0001), while in trisomy 21 fetuses prediction was provided by CRL (OR, 0.94; 95% CI, 0.89-0.99; P = 0.021). The likelihood ratio for trisomy 21 for tricuspid regurgitation was derived by dividing the likelihood in trisomy 21 by that in normal fetuses. In the chromosomally normal fetuses, the prevalence of tricuspid regurgitation in those with cardiac defects was 46.9% and 5.6% in those without cardiac defects, and the likelihood ratio of tricuspid regurgitation for cardiac defects was 8.4. CONCLUSION: At 11 to 13 + 6 weeks' gestation, there is a high association between tricuspid regurgitation and trisomy 21, as well as other chromosomal defects. The prevalence of tricuspid regurgitation increases with fetal NT thickness and is substantially higher in those with, than those without, a cardiac defect.     

Fetal nasal bone length: reference range and clinical application in ultrasound screening for trisomy 21.

OBJECTIVES: Fetuses with trisomy 21 typically present with subtle facial abnormalities, including a hypoplastic nasal bone. The aim of this study was to provide a reference range for the length of the fetal nasal bone and to test its value in second-trimester ultrasound screening for trisomy 21. DESIGN: A reference range of fetal nasal bone length was established from cross-sectional data on 1923 consecutive singleton pregnancies scanned at 16-24 weeks' gestation in women older than 35 years. Screening for trisomy 21 was prospectively studied using the measurement of fetal nasal bone lengths smaller than the 5(th) percentile as a cut-off value. RESULTS: Follow-up was possible in 1631 cases (84.8%). Trisomy 21 was found in 22 cases (1.35%). Nasal bone length measurement increased as a function of gestational age (P < 0.05) showing a linear relationship. Screening for trisomy 21 using the 5(th) percentile as a cut-off value resulted in a sensitivity of 59.1% for a 5.1% false-positive rate. The likelihood ratio was 11.6. CONCLUSION: Screening for trisomy 21 using fetal nasal bone length measurements showed a sensitivity comparable to that of maternal biochemistry for a given false-positive rate of 5%. Association of nasal bone lengths with other sonographic markers, taking into account the background risk for maternal and gestational age, may further improve sensitivity and reduce false positives, allowing avoidance of unnecessary invasive diagnostic procedures.     

超声评价胎儿鼻骨的价值

超声在孕11～13^＋6周即可显示胎儿鼻骨。研究表明,鼻骨缺少与21-三体及其它染色体异常有很高的相关性。鼻骨检查结合母血生化测定综合筛查可使21-三体综合征的检出率上升到95％以上。