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.     

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.     

Vesicocentesis at 10-14 weeks of gestation for treatment of fetal megacystis.

This report of four cases shows that fetal vesicocentesis at 10-14 weeks of gestation is a useful treatment option in some cases with megacystis. Although megacystis at this gestation has been reported, there are few studies examining the role of early vesicocentesis. The natural history of the condition and outcome following treatment is reviewed with reference to the literature.     

The sonographic identification of fetal gender from 11 to 14 weeks of gestation.

OBJECTIVE: To determine the feasibility of correctly identifying fetal gender from 11 to 14 weeks' gestation. METHODS: A prospective cross-sectional study in a university Department of Obstetrics and Gynaecology, London. A total of 524 women from an unselected population underwent a detailed assessment of fetal anatomy at 11-14 weeks of gestation (confirmed by crown-rump length) by means of transabdominal sonography, and transvaginal sonography (26%) when necessary. Fetal gender was identified in the transverse and sagittal planes, and was confirmed at birth. RESULTS: The overall success of correctly assigning fetal gender increased with gestational age from 46% to 75%, 79% and 90% at 11, 12, 13 and 14 weeks, respectively. The ability of the operator to assign fetal gender significantly improved with increasing gestational age (p < 0.0001), being 59%, 87%, 92% and 98% at 11, 12, 13 and 14 weeks, respectively. The accuracy of correctly identifying fetal gender when attempted did not change with gestational age. Fetal gender or the performance of the scan by different operators did not affect the results. CONCLUSION: Whilst the accuracy of sonographic determination of fetal gender at 11-14 weeks is good, it still falls significantly short of invasive karyotyping tests.     

Megacystis at 10-14 weeks of gestation: chromosomal defects and outcome according to bladder length.

AIMS: To examine the prevalence of chromosomal defects and outcome of fetuses with megacystis at 10-14 weeks of gestation. METHODS: At the 10-14-week scan fetal megacystis was defined by a longitudinal bladder diameter of 7 mm or more. In 145 such fetuses the fetal karyotype and pregnancy outcome were examined in relation to the longitudinal diameter of the fetal bladder. RESULTS: Chromosomal defects, mainly trisomies 13 and 18, were present in 30 cases. In the group with longitudinal bladder diameter of 7-15 mm the incidence of chromosomal defects was 23.6% (26/110), whereas in those with bladder diameter > 15 mm the incidence was 11.4% (4/35). The fetal nuchal translucency (NT) was above the 95th centile of the normal range for crown-rump length in a higher proportion of cases with abnormal rather than normal karyotype (76.7% compared to 31.3%; Chi-square P < 0.0001). The expected number of cases of trisomy 21, estimated on the basis of maternal age, gestational age and fetal NT, was 6.2 rather than the observed 2 and the corresponding numbers for trisomies 13 or 18 were 4.2 for expected and 24 for observed. In the chromosomally normal group with longitudinal bladder diameter of 7-15 mm follow-up scans demonstrated spontaneous resolution of the megacystis in 90% of the cases and enlargement of the megacystis and/or the development of echogenic kidneys in 10%. In contrast, none of the cases with bladder diameter > 15 mm demonstrated spontaneous resolution of the megacystis. CONCLUSIONS: In fetal megacystis with longitudinal bladder diameter of 7-15 mm there is a risk of about 25% that the fetus will have a chromosomal defect but in the chromosomally normal group there is spontaneous resolution of the megacystis in about 90% of cases. If the bladder diameter is > 15 mm the risk of chromosomal defects is about 10% and in the chromosomally normal group the condition is invariably associated with progressive obstructive uropathy.     

Reference values for fetal limb biometry at 10-14 weeks of gestation.

OBJECTIVES: To calculate reference ranges for fetal limb measurements obtained by transabdominal ultrasound at 10-14 weeks of gestation. METHODS: Six hundred and six normal fetuses were examined transabdominally in a cross-sectional study by a single observer. The crown-rump length of the fetuses ranged from 31 to 78 mm. Measurement of the length of the humerus, ulna, femur, tibia and foot was attempted from the longest section of each structure. To assess intraobserver repeatability, three sets of repeated measurements were obtained in 26 fetuses. RESULTS: An appropriate ultrasound measurement was obtained in a percentage of cases ranging from 93.2% to 97.9%. A significant correlation was found between crown-rump length measurements and humerus length (r = 0.74, P < 0.001), ulna length (r = 0.70, P < 0.001), femur length (r = 0.77, P < 0.001), tibia length (r = 0.69, P < 0.001) and foot length (r = 0.58, P < 0.001). Crown-rump length-specific reference ranges for each measurement were calculated with the method of scaled absolute residuals. The study of intraobserver variability showed coefficients of variation ranging from 7.9 to 10.0% and intraclass correlation coefficients ranging from 0.89 to 0.94. CONCLUSIONS: Fetal limb size is strongly correlated with crown-rump length. Despite a significant biological variability of the measurements, the availability of reference ranges could be of help in the early diagnosis of fetal skeletal dysplasias.     

Disappearance of enlarged nuchal translucency before 14 weeks' gestation: relationship with chromosomal abnormalities and pregnancy outcome.

OBJECTIVE: The aim of this study was to investigate the natural course of enlarged nuchal translucency (NT) and to determine if its disappearance before 14 weeks' gestation is a favorable prognostic sign in relation to fetal karyotype and pregnancy outcome. METHODS: A total of 147 women with increased NT (> 95th centile) at first measurement were included in this study. A second measurement was performed in all cases, at an interval of at least 2 days. Both measurements were taken between 10 + 3 and 14 + 0 weeks. All women underwent chorionic villus sampling or amniocentesis for subsequent karyotyping. In those women with a normal karyotype, a fetal anomaly scan was performed at 20 weeks' gestation. Pregnancy outcome was recorded in all cases. The finding of persistent or disappearing NT enlargement was analyzed in relation to fetal karyotype and pregnancy outcome. RESULTS: Of the 147 paired measurements, NT remained enlarged at the second measurement in 121 (82%) cases. An abnormal karyotype was found in 35% of these cases. In 26 (18%) fetuses the NT measurement was found to be below the 95th percentile at the second measurement and in only two of them an abnormal karyotype was found (8%). In the 103 chromosomally normal fetuses an adverse outcome (i.e. fetal loss or structural defects) was recorded in 22 fetuses with persistent enlargement (28%) and in four fetuses with disappearing enlargement (17%). CONCLUSIONS: Disappearance of an enlarged NT before 14 weeks' gestation is not a rare phenomenon and seems to be a favorable prognostic sign with respect to fetal karyotype. Overall, no significant difference in pregnancy outcome was found between chromosomally normal fetuses with persisting or disappearing NT enlargement.     

Ductus venosus blood flow assessment at 11 to 14 weeks of gestation and fetal outcome.

OBJECTIVE: To evaluate the association between abnormal ductus venosus (DV) at 11-14 weeks' gestation and chromosomal abnormalities, structural defects and fetal outcome. METHODS: DV flow-velocity waveform (DV-FVW) and nuchal translucency thickness (NT) were prospectively evaluated in 1217 singleton pregnancies. RESULTS: The DV-FVW was abnormal in 84 fetuses, NT was above the 95th centile in 160 fetuses and both markers were observed in 41 fetuses. Chromosomal defects were diagnosed in 22 fetuses. The sensitivity, specificity and positive and negative predictive values for an abnormal karyotype were 86.4%, 86.9%, 11.9% and 99.7%, respectively, for an increased NT. These values were 68.2%, 96.9%, 31.3% and 99.3%, respectively, for DV-FVW abnormalities and 68.2%, 97.6%, 36.6% and 99.3%, respectively, when both markers were found simultaneously. Regarding structural defects, these values were 43.8%, 92.9%, 8.3% and 99.1% for an abnormal NT, 25.0%, 92.6%, 4.8% and 98.8% for DV-FVW abnormalities and 25.0%, 97.9%, 15.4% and 98.9% for both together. Considering those cases of unexplained fetal demise, the values were 44.4%, 85.9%, 5.0% and 98.9% for NT abnormalities, 22.2%, 92.6%, 4.8% and 98.6% for an abnormal DV-FVW and 22.2%, 98%, 15.4% and 98.7% for both. In cases with increased NT, the percentage of live births with normal karyotype and no major fetal structural defects decreased from 93.8% in normal DV-FVW fetuses to 77.3% in abnormal ones. CONCLUSION: DV assessment at 11-14 weeks' gestation is useful in screening for fetal chromosomal abnormalities and may help to reduce the false-positive rate when combined with NT measurement. Abnormal DV-FVW is also associated with an increase in adverse perinatal outcome in fetuses with enlarged NT. However, the value of DV-FVW assessment in cases with normal NT is unclear.     

中、晚孕期超声筛查胎儿染色体异常

目的 探讨中、晚孕期超声筛查胎儿染色体异常的价值.方法 在妊娠中期和晚期,分别对有产前诊断指征的2955名和173名孕妇行羊水和脐血穿刺术检查染色体核型,比较不同指征孕妇的异常核型检出率,并分析染色体异常与超声异常的关系.结果 接受羊水穿刺的2955名孕妇中,异常核型150名,异常率5.08%;超声异常91名,异常核型11名,异常率12.09%;超声异常组染色体异常检出率(12.09%)明显高于唐氏高危组(4.46%)、高龄孕妇组(3.89%)、不良孕产史组(2.74%)(P＜0.05).173名脐血染色体核型分析中,26名为异常核型,异常率15.03%;超声异常118名,异常核型16名,异常率13.56%.结论 中、晚孕期超声筛查胎儿染色体异常有很大价值.     

经阴道超声对11~14孕周胎儿结构异常的诊断价值

目的 探讨经阴道彩色超声检查在11～14孕周诊断胎儿结构异常的价值。方法 对75例11～14孕周有高危妊娠病史或经腹检查不满意以及经腹检查怀疑胎儿有异常的孕妇进行了经阴道彩色超声检查，并与胎儿引产结果对照。结果 在75例受检胎儿中，发现胎儿结构异常12例，随访9例，除1例足内翻漏诊外，均与阴道彩超检查结果符合。结论 经阴道彩超检查对早期诊断胎儿结构异常有重要临床应用价值。     

经阴道超声对11~14孕周胎儿结构异常的诊断价值

目的探讨经阴道彩色超声检查在11～14孕周诊断胎儿结构异常的价值.方法对75例11～14孕周有高危妊娠病史或经腹检查不满意以及经腹检查怀疑胎儿有异常的孕妇进行了经阴道彩色超声检查,并与胎儿引产结果对照.结果在75例受检胎儿中,发现胎儿结构异常12例,随访9例,除1例足内翻漏诊外,均与阴道彩超检查结果符合.结论经阴道彩超检查对早期诊断胎儿结构异常有重要临床应用价值.     

Intra- and interoperator variability in fetal nasal bone assessment at 11-14 weeks of gestation.

OBJECTIVES: Examination of the fetal nasal bones by ultrasound between 11 and 14 weeks of gestation has been proposed as an additional tool in the detection of trisomy 21 in a high-risk population. However the variability in the identification of fetal nasal bones by ultrasound has not yet been investigated. The aim of this study was to assess the intraobserver and interobserver reproducibility of fetal nasal bone identification by ultrasound between 11 and 14 weeks of gestation. METHODS: A total of 1040 consecutive ultrasound examinations were performed at 11-14 weeks of gestation for nuchal translucency (NT) measurement and nasal bone identification by ultrasound. A total of 657 consecutive video-loops were assessed by three experienced operators. Each operator assigned cases to one of three categories, namely present, uncertain or absent nasal bones, and the results were compared between operators. To assess the intraoperator variability each operator reviewed 100 randomly selected videos out of the 657 loops and again used the same classification. Results were compared by pairwise unweighted and weighted Kappa index to evaluate the inter- and intraoperator variability. RESULTS: Among the 1040 fetuses, there were 51 (4.9%) with an NT measurement above the 95th centile. Nasal bones were identified by ultrasound in 948, not seen in eight and impossible to assess in 84 fetuses. Four fetuses had trisomy 21 including three with absent nasal bones and increased NT and one with present nasal bones and normal NT. The Kappa and weighted Kappa values for interoperator variability between the three operators were between 0.26 and 0.37 and 0.33 and 0.44, respectively. The Kappa and weighted Kappa values for intraoperator variability were between 0.35 and 0.48 and 0.43 and 0.55, respectively. CONCLUSION: The assessment of fetal nasal bones is only fairly reproducible. Although the performance of the test in fetuses at high risk for trisomy 21 has been reported to be good, its implementation as an additional screening technique in the general population must be accompanied by teaching and quality control programs.     

Early fetal megacystis between 11 and 15 weeks of gestation.

OBJECTIVE: The purpose of this study was to evaluate the prognostic criteria of early fetal megacystis. DESIGN: A prospective, transvaginal ultrasound, cross-sectional study at 11-15 weeks of gestation at a tertiary referral fetal medicine unit. SUBJECTS AND METHODS: Sixteen pregnancies out of a total of 5240 were identified with early fetal megacystis. Fetal biometry, morphology, amniotic fluid, bladder size and volume were also evaluated. The karyotype was available in 15 cases. Vesicocentesis was performed in six fetuses and three had concomitant cystoscopies. RESULTS: In six fetuses, the megacystis was isolated. In the remaining ten, we detected associated hygroma (n = 5), nuchal translucency (n = 3), omphalocele (n = 1), mild pyelectasis (n = 1) and bilateral talipes (n = 1). In three cases the fetuses demonstrated renal hyperechogenicity with cysts, and in two cases oligohydramnios was found; four cases (25%) had chromosomal abnormalities; 47, XY + 13 (two cases), 47, XY + 18 and 47, XY + 21. Only one fetus from this study survived. In the remaining 13 cases, termination was proposed after counselling of the patients on the poor prognosis. The mean gestational age at termination was 15.5 +/- 2.4 weeks (range 12-20). Three fetal transabdominal cystoscopies did not allow us to view the valves; one urethral atresia was suspected, and confirmed postnatally. CONCLUSIONS: We found a high rate of associated malformations, especially intestinal malformations. The systematic evaluation of the intestinal enzymes in the amniotic fluid and urine samples might be an important aid in the diagnosis of multiple malformations, such as cloacal dysgenesis.     

Assessment of the fetal nasal bone at 11-14 weeks of gestation by three-dimensional ultrasound.

OBJECTIVE: To evaluate the benefit of three-dimensional (3D) ultrasound in the examination of the fetal nasal bone at 11-14 weeks of gestation. METHOD: We examined the fetal nasal bone in 120 stored volumes acquired transabdominally with a 3D scanner from singleton pregnancies at 11-14 weeks of gestation. The volume acquisition had been performed following conventional ultrasound examination that had demonstrated presence of the fetal nasal bone. The volumes were obtained with two-dimensional (2D) start images in transverse, coronal mid-sagittal, parasagittal and oblique longitudinal sections of the fetal head. RESULTS: In the transverse and coronal sections, a satisfactory image demonstrating presence of the nasal bone was achieved in only three and one, respectively, of the 20 volumes that we obtained. In mid-sagittal sections, the nasal bone was always visible when the angle was within a range of 30-60 degrees, without the need for sectional image analysis. None of the images with an angle >60 degrees or <30 degrees was satisfactory. In the parasagittal sections with the fetal profile at 45 degrees, a good-quality image of the nasal bone was possible in all cases that were examined, irrespective of the distance from the mid-sagittal plane. In the oblique longitudinal sections with the fetal profile at 45 degrees, there were 10 volumes where the 2D start section was at 0-25 degrees from the midline and in all these cases the nasal bone was successfully visualized. In contrast, only 5/20 cases where the 2D start section was at 25-90 degrees from the midline provided a satisfactory image demonstrating the nasal bone. In 5/10 volumes obtained with the fetus facing downwards the nasal bone was visible in both the 2D and 3D images. CONCLUSION: In a 3D volume the extent to which the nasal bone can be demonstrated to be present in a given reconstructed section is entirely dependent on obtaining a good initial 2D view.     

Fetal exomphalos at 11 to 14 weeks of gestation.

In an ultrasonographic screening study at 11 to 14 weeks' gestation involving 9885 singleton pregnancies, the prevalence of exomphalos was 0.11% (11 cases) and the prevalence of trisomy 18 or 13 was 0.35% (35 cases). The mean maternal age of the screened population was 35 years (range, 15 to 47 years) and a significant association was found between maternal age and both the prevalence of trisomies and the prevalence of exomphalos. Because the frequency of exomphalos in fetuses with trisomy 18 or 13 was 17% and in those with no evidence of these trisomies it was 0.05%, the risk for trisomies in fetuses with exomphalos is 340 times higher than in those without exomphalos.     

Screening for pre-eclampsia and fetal growth restriction by uterine artery Doppler at 11-14 weeks of gestation.

OBJECTIVE: To examine the value of uterine artery Doppler at 11-14 weeks of gestation in the identification of women at risk of developing pre-eclampsia and fetal growth restriction. METHODS: Uterine artery Doppler was carried out at 11-14 weeks in 3324 consecutive singleton pregnancies attending for routine care in three London hospitals. The right and left uterine arteries were identified using color flow mapping and velocity waveforms were obtained using pulsed Doppler. The mean pulsatility index of the two arteries was determined and the predictive value of a mean pulsatility index > the 95th centile in the prediction of pre-eclampsia and/or fetal growth restriction was calculated. RESULTS: Satisfactory flow velocity waveforms were obtained from both uterine arteries in 3195 (96.1%) of the 3324 pregnancies examined and complete outcome information was obtained for 3045 (95.3%) of these women. The 95th centile of the uterine artery mean pulsatility index was 2.35 and did not change significantly with gestational age. The pregnancy was complicated by pre-eclampsia in 63 (2.1%) cases and by fetal growth restriction in 290 (9.5%) cases. The sensitivity of a mean pulsatility index > 2.35 for pre-eclampsia (with or without fetal growth restriction) was 27.0% but for fetal growth restriction alone it was 11.7%. The respective sensitivities for these complications requiring delivery before 32 weeks of gestation were 60.0% and 27.8%, respectively. CONCLUSION: Uterine artery Doppler at 11-14 weeks of gestation identifies a high proportion of women who develop severe pre-eclampsia and/or fetal growth restriction.     

Fetal transabdominal biometry at 11-14 weeks of gestation.

OBJECTIVE: To establish comprehensive transabdominal ultrasonographic reference ranges for viable normal singleton human fetuses at 11-14 weeks' gestation. METHODS: Single transabdominal ultrasound measurements were taken once per pregnancy at a gestational age of between 11+0 and 14+0 weeks (crown-rump length, 45-84 mm), in viable singleton fetuses with nuchal translucency < or = 3 mm and without detectable structural anomalies, using four standard planes: (i) biparietal diameter (BPD) and fronto-occipital diameter (FOD) resulting in head circumference (HC), anterior horn (Va), posterior horn (Vp), and hemisphere (HEM); (ii) transcerebellar diameter (TCD) and cisterna magna (CM); (iii) abdominal anteroposterior (AAP) and abdominal transverse diameter (ATD) resulting in abdominal circumference (AC); and (iv) femur length (FL). The respective ratios Va/HEM, Vp/HEM, HC/AC, BPD/FL, BPD/FOD, FL/CRL, FL/BPD and FL/AC and the estimated weight were derived. Reference ranges were constructed and the mean and 5th and 95th centiles were plotted against gestation. RESULTS: There was a general increase in biometric parameters with gestation. The ratios for the ventricles vs. hemisphere and BPD/FL ratio decreased while the BPD/FOD and HC/AC ratios remained constant. Analysis of the reference range for BPD/FL was performed in both 167 and 664 fetuses and the results showed almost the identical type of equation, indicating a high degree of accuracy for the growth charts. CONCLUSIONS: We have established comprehensive reference ranges for first-trimester fetal biometry by transabdominal sonography. These charts may have a role in the diagnosis of early onset symmetrical or asymmetrical growth restriction and in the interpretation of measurements in chromosomally abnormal fetuses, and they may help in the detection of skeletal dysplasias or acrania/anencephaly.