Diagnostic ultrasound: early detection of fetal neural tube defects

In a series of 366 patients identified as at risk for a fetal neural tube defect (NTD) before the 24th week of pregnancy, 64 had an abnormal fetus. The abnormalities included anencephaly (39), open spinal defect (17), closed spinal defect (2), encephalocele (1), and a miscellany of other abnormalities (5). An ultrasound examinaton prior to diagnostic anmiocentesis positively identified all anencephalic fetuses, the fetus with the encephalocele, and 15 of the 19 fetuses with spina bifida. The spinal defects in 3 of the remaining 4 fetuses were demonstrated at a second examination. Since both amniotic fluid alpha-fetoprotein (AFP) assays and ultrasound examination have been shown to give false results in the diagnosis of NTDs, the importance of using 2 independent diagnostic techniques is stressed. In patients with elevated levels of maternal serum AFP, a careful ultrasound examination, in addition to identifying the majority of cases associated with an abnormal fetus, provided a good explanation for the elevation in over half of the remainder. In this series more than half the patients (40/69) who underwent amniocentesis because of raised maternal serum AFP levels were shown to have an abnormal fetus.     

胎儿颈项透明层增厚和静脉导管血流频谱异常与胎儿染色体异常的关系

目的探讨胎儿颈项透明层(nuchal translucency, NT)超声检查在早孕期胎儿筛查中的应用价值。 方法收集104例于广州市妇女儿童医疗中心诊断NT增厚的孕妇的染色体核型分析资料,回顾性分析胎儿NT增厚、静脉导管血流频谱异常与胎儿染色体异常的关系。 结果(1)9980例孕妇中,NT异常增厚的胎儿共104例,占1.0%,颈项透明层厚度为(3.7±1.2)mm;(2)104例NT异常增厚的胎儿中,有28例胎儿染色体核型异常,包括染色体数目异常22例,结构异常6例,其中前3位为21-三体综合征、18-三体综合征和47,XXX;(3)随着NT厚度的增加,染色体异常的检出率相应增加;(4)NT增厚及静脉导管血流频谱正常预测染色体异常的阳性预测值是20.93%,NT增厚及静脉导管血流频谱异常的阳性预测值是55.56%,其差异具有统计学意义( χ²＝7.07,P<0.01)。 结论在早孕期进行胎儿NT超声检查,NT增厚及静脉导管血流频谱异常联合筛查更能有效筛查出染色体核型异常的高危胎儿。     

Fetal anomaly scan potentially will replace routine AFAFP assays for the detection of neural tube defects

OBJECTIVES: Introduction of the second-trimester fetal anomaly scan and the decision to offer this scan to every woman in the 18th-22nd week of pregnancy necessitates a re-evaluation of the diagnostic value of the measurement of alpha-fetoprotein (AFP) concentrations in the amniotic fluid (AF) for the detection of neural tube defects (NTDs). METHODS: In this study of 6501 women who underwent amniocentesis, amniotic fluid AFP (AFAFP) concentrations were measured. The women were divided into three categories: group I, without any increased risk of fetal NTD (N = 6188); group II, with an increased risk of fetal NTD (N = 258); and group III, with a clinically diagnosed fetal NTD with known AFAFP concentrations (N = 55). RESULTS: In 27 women of group I (0.4%), the MoM (multiple of the median) level was > 2.5 times the median AFP concentration for the corresponding gestational age, and in two fetuses this was related to NTD. In two pregnancies of group II (0.8%), an increased AFAFP was related to NTD. In group III, 44 of the 55 (80%) samples had an increased AFAFP. CONCLUSION: In the near future, it is likely that imaging will replace AFAFP assays for the detection of fetal NTDs because high quality ultrasound imaging will detect NTDs accurately.     

Chromosomal anomalies and additional sonographic findings in fetuses with open neural tube defects

Objective

To evaluate the results and the necessity of chromosome analysis in fetuses prenatally detected with a neural tube defect and to determine the significance of ultrasonographic evaluation for the identification of underlying or accompanying chromosomal anomalies.

Methods

Ninety fetuses that underwent prenatal and/or postnatal chromosome analysis after being diagnosed with open neural tube defects (NTD) between the years 2006 and 2010 in the Department of Obstetrics and Gynecology at Ondokuz Mayis University School of Medicine were included in this study. Detailed fetal ultrasonography was performed in all cases in order to investigate any additional anomalies. Karyotype was determined in the prenatal period by amniocentesis in 72 (80?%) of the 90 fetuses, and by cordocentesis in 5 (5.5?%). In 13 (13.3?%) fetuses, karyotype was determined in the postnatal period by blood sampling.

Results

Fourteen (15.5?%) of the 90 fetuses were diagnosed with acrania/anencephaly, 14 (15.5?%) with encephalocele, 2 (2.2?%) with iniencephaly, 60 (66.6?%) with open spina bifida. None of the 90 fetuses with open NTD who had undergone chromosome analysis was diagnosed with chromosomal anomalies. None of the 19 (21.1?%) fetuses diagnosed with additional ultrasound findings had a chromosomal abnormality, either. Seventy-one (78.9?%) fetuses having sonograhically isolated NTD were also isolated in postmortem examination.

Conclusion

In fetuses with open NTD, we could not find the chromosomal anomaly rate as high as reported in previous literature. The necessity of fetal karyotyping should be questioned especially in isolated cases.     

Chromosomal abnormalities associated with neural tube defects (I): full aneuploidy

Fetuses with neural tube defects (NTDs) carry a risk of chromosomal abnormalities. The risk varies with maternal age, gestational age at diagnosis, association with other structural abnormalities, and family history of chromosome aberrations. This article provides an overview of chromosomal abnormalities associated with NTDs in embryos, fetuses, and newborn patients, and a comprehensive review of numerical chromosomal abnormalities associated with NTDs, such as trisomy 18, trisomy 13, triploidy, trisomy 9, trisomy 2, trisomy 21, trisomy 7, trisomy 8, trisomy 14, trisomy 15, trisomy 16, trisomy 5 mosaicism, trisomy 11 mosaicism, trisomy 20 mosaicism, monosomy X, and tetraploidy. NTDs may be associated with aneuploidy. Perinatal identification of NTDs should alert one to the possibility of chromosomal abnormalities and prompt a thorough cytogenetic investigation and genetic counseling.     

Amniotic fluid alpha-fetoprotein levels and the prenatal diagnosis of neural tube defects: a collaborative study of 2180 pregnancies in the Netherlands.

Amniotic fluid alpha-fetoprotein (AFP) concentrations were measured in 2180 patients at risk of fetal abnormality because of previous history, family history, advanced maternal age, suspected fetal growth retardation and hydramnios. In 12 patients investigated before 20 weeks gestation, pregnancy was terminated because of a raised amniotic fluid AFP-level: 11 fetuses had neural tube defects (NTDs) and one had a congenital nephrosis. There were no false negative results in the 1927 patients tested before 20 weeks and with a pregnancy of known outcome. In patients tested after 20 weeks, the amniotic fluid AFP concentration was raised in 20 cases of anencephaly, in 9 fetuses with severe congenital malformations without NTD and in one apparently normal fetus. Of 428 patients with a previous offspring who had a NTD, only 8(1.9 per cent) again had a fetus with a NTD.     

Prenatal genetic diagnosis in 350 amniocenteses.

Three hundred and fifty second trimester amniocenteses performed for prenatal diagnosis of genetic disorders are reported. One hundred and ninety-three of these were performed because maternal age was greater than 35 years, and 6 fetuses with unbalanced chromosomal abnormalities (3%) were identified. Thirteen procedures were performed because a previous child had had a neural tube defect; 1 anencephalic fetus was identified. Ninety-six percent of the initial taps were cultured successfully; we failed to obtain amniotic fluid in 3% of patients. The risk of a spontaneous abortion occurring at some time after the amniocentesis was 0.85%, and no cases of fetal injury were identified.     

Umbilical cord diameter at 11-14 weeks of gestation: relationship to nuchal translucency, ductus venous blood flow and chromosomal defects

OBJECTIVE: To compare the umbilical cord diameter (UCD) in euploid and aneuploid fetuses at 11-14 weeks of gestation. METHODS: In 299 fetuses at 11-14 weeks of gestation the UCD, the nuchal translucency and the a-wave of the ductus venosus were measured. Reference ranges for the UCD according to the gestational age and to the crown-rump-length (CRL) were obtained by measuring the UCD by outer-to-outer border of 244 singleton pregnancies with normal karyotype. The fetal karyotype was established by chorionic villus sampling, amniocentesis or in case of suspected chromosomal abnormalities in the newborn. Linear regression was used to determine the significance of the association between the UCD and CRL or gestational age. RESULTS: Two hundred and ninety-nine fetuses were examined. The median fetal CRL was 64.5 mm (range 45-84) and the median gestational age was 13 (range 11-14) weeks. In the chromosomally normal group the UCD significantly increased with the CRL (r=0.620; p<0.001) and the gestational age (r=0.555; p<0.001). The regression equation for the mean UCD (y) according to the gestational days (x) was: y=-0.604+0.051*x. The regression equation for the mean UCD (y) according to the CRL (x) was: y=1.962+0.029*x. There were no significant differences in the mean UCD in fetuses without and with chromosomal abnormalities. The proportion of fetuses with an UCD above the 95th centile for CRL was higher in aneuploid compared to euploid fetuses (5/14 vs. 13/285, p<0.005). In 5/14 (35.7%) fetuses with chromosomal defects the NT and the UCD were above the 95th centile, whereas none of the fetuses with normal karyotype showed this combination. The proportion of fetuses with increased UCD and abnormal DV blood flow was increased in the cases with chromosomal abnormalities (33.3 vs. 1.8%, p<0.005). CONCLUSION: Umbilical cord diameter at 11-14 weeks increases with fetal CRL. Fetuses with chromosomal abnormalities are more likely to have an UCD above the 95th centile. Therefore, sonographic evaluation of the umbilical cord during first trimester ultrasound might be of additional value in the assessment of fetuses at risk for aneuploidies.     

Should determination of the karyotype be systematic for all malformations detected by obstetrical ultrasound?

OBJECTIVE: The aim of this study was to determine whether karyotyping should be performed for every fetal malformation detected in low risk populations. METHODS: A karyotype was obtained from 428 fetuses examined over a 10-year period after fetal malformation was diagnosed using obstetrical ultrasound. These fetuses were separated into two groups, one with isolated malformations and the other with multiple malformations. The association between each type of malformation and the result of karyotype was evaluated. RESULTS: Forty-eight chromosomal abnormalities were encountered in 428 fetuses (11.2%). The karyotype was abnormal in 32/343 (9.3%) fetuses with isolated malformations and 16/85 (18.8%) fetuses with multiple malformations (p=0.022). The probability of an abnormal karyotype among the group of isolated malformation depended on the anatomical system involved (p<0.001). Our study demonstrated several isolated malformations without chromosomal abnormality (hydronephrosis with high obstruction, unilateral multicystic dysplastic kidney, gastroschisis, intestinal dilatation, meconium peritonitis, cystic adenomatoid malformation, pulmonary sequestration, tumor, vertebral anomaly). CONCLUSION: Each fetus with multiple malformations needs a chromosomal analysis. Within the group of isolated malformations, our study emphasizes that medical maternal history and the type of malformation need to be taken into account before performing a fetal karyotype.     

Chromosomal defects and associated malformations in fetal cleft lip with or without cleft palate

OBJECTIVE: To describe the incidence, associated features including chromosomal defects in fetuses, with cleft lip and/or palate and assess the need for karyotyping. METHODS: Retrospective study of 62 cases of prenatally diagnosed facial cleft lip and/or palate in a tertiary fetal medicine unit between January 1991 and December 1999. Chromosome analysis was performed in all fetuses with associated ultrasound findings and in 14 (39%) fetuses with isolated facial clefts. RESULTS: Associated abnormalities were detected in 26 (42%) of the 62 fetuses of which 22 (35%) fetuses had multiple other abnormalities. Central nervous system abnormalities and limb malformations were the most common. Three fetuses had genetic syndromes confirmed after birth. All fetuses with isolated clefts were chromosomally normal, whereas 15 of the 26 with additional abnormalities (58 or 24% of the total group) had chromosomal defects (eight cases of trisomy 13, five of trisomy 18, one unbalanced translocation between chromosomes 7 and 8, and one deletion 4p-). All 22 women who chose not to undergo fetal karyotype analysis delivered phenotypically normal infants. There were five midline clefts; each of them was associated with additional sonographic findings and four were associated with holoprosencephaly. CONCLUSION: Isolated facial clefting is not associated with an increased risk for chromosomal defect. Amniocentesis is recommended when facial cleft is found in association with additional ultrasonographic abnormalities as it is unnecessary for isolated clefts.     

2178对自然流产史夫妇染色体分析

目的:分析自然流产史夫妇外周血染色体异常核型的种类及其在男女性中的分布特点。方法:检测2178对自然流产史夫妇外周血淋巴细胞染色体核型,分析比较染色体变异的种类、发生率及其在男、女性中的分布差异。结果:2178对(4356例)自然流产史夫妇中发现染色体异常539例(12.37%),其中男266例,女273例。染色体结构异常87例,其中相互易位最多见为58例(66.7%,58/87),有27例为世界首报染色体结构异常核型。其次为罗伯逊易位13例,倒位6例,插入、缺失等其他异常核型10例。染色体数目异常8例,包括2例标记染色体、1例XYY及5例不同类型的X染色体非整倍体嵌合。多态性改变444例中,D/G组染色体随体区变异最为多见,共271例(61.04%,271/444)。结论:自然流产史夫妇外周血染色体异常均有发生,男女性发生率并无明显差异,染色体异常以相互易位为主。染色体多态性发生率较高,对以自然流产史就诊的夫妇,有必要同时进行染色体检查,有助于病因的分析与诊断,并为临床咨询及后续生殖干预提供依据。     

Fetal obstructive uropathies. Importance of chromosomal abnormalities and associated anomalies to perinatal outcome.

The ultrasound records of 30 fetuses suspected of having an obstructive uropathy were reviewed retrospectively. A prenatal karyotype was obtained with amniocentesis on each patient. After delivery, neonatal urologic records, renal ultrasound reports and autopsy information were reviewed and compared to the ultrasound records and fetal karyotype results. Chromosomal defects were found in 23% of fetuses with a suspected obstructive fetal uropathy. In five patients the chromosomal abnormality was lethal and caused 45% of the perinatal deaths in this series. If a fetus with an obstructive uropathy was female, there was a significant likelihood of an extrarenal anomaly or a complex genitourinary tract malformation. Seventeen percent of patients with an obstructive uropathy had a coexistent extrarenal defect. A prenatal karyotype should be obtained if a fetal obstructive uropathy is suspected antenatally since lethal chromosomal defects are an important cause of perinatal death. A female karyotype may indicate a fetus at higher risk of extrarenal anomalies or complex genitourinary malformations.     

First-trimester ductus venosus velocimetry in relation to nuchal translucency thickness and fetal karyotype.

AIM: To evaluate first-trimester ductus venosus flow in relation to nuchal translucency (NT) and fetal karyotype. METHODS: Ductus venosus flow was measured in fetuses with NT greater than or equal to the 95th centile (group A) and in fetuses with NT less than the 95th centile (group B). The waveforms were classified as normal if the lowest forward velocity during atrial contraction (ACV) was positive and abnormal if it was absent or negative. The results were compared with the fetal karyotype. RESULTS: Ductus venosus measurement was carried out in 330 fetuses. In group A, there were 156 fetuses: in 4 cases, it was not possible to obtain the measurement, and in the other 152 cases, 93 (61%) had a normal ACV and 59 (39%) an abnormal ACV. NT thickness was significantly greater in fetuses with abnormal ACV. In 34 out of 156 cases (22%), chromosomal abnormalities were found. Twenty-three chromosomopathies out of 33 (70%) had an abnormal ACV, and 10 (30%) had a normal ACV. A significant association between abnormal karyotype and abnormal ACV was found. Ductus venosus measurement was carried out in 174 fetuses of group B. In 1 case, it was not possible to obtain the measurement. One hundred and seventy-one (99%) cases had a normal ACV, and in 2 (1%) cases the ACV was abnormal. No chromosomal abnormalities were found in group B. Considering group A and group B, a significant association between the finding of an enlarged NT and abnormal ACV was detected (p < 0.05). CONCLUSIONS: An abnormal ACV is more frequent in fetuses presenting enlarged NT than in those having normal NTs and in fetuses having the larger nuchal thickness. The probability of having a chromosomal abnormality in fetuses with enlarged NT is greater when an abnormal ACV is found.     

孕妇血浆中胎儿DNA检测在产前诊断中的应用

目的 探讨孕妇血浆中提取胎儿游离DNA,鉴别胎儿性别以诊断胎儿遗传性疾病的方法。方法 选择妊娠7-38周,B超确诊为单胎,经绒毛和羊水细胞染色体检测,确诊为妊娠男性胎儿的正常孕妇16例,妊娠女性胎儿的正常孕妇8例;X性连锁遗传病（假性肥大性肌营养不良,血友病,色盲,无汗性外胚层发育不良症）家族史行产前诊断者4例,用酚提取法,纯化孕妇血浆中胎儿DNA,然后用巢式聚合酶链反应（PCR）技术测定男性胎儿睾丸决定因子（SRY）。结果 16例妊娠男性胎儿孕妇血浆中,胎儿游离DNA第1次巢式PCR测定,检出SRY基因扩增片段10例,第1次检出率为62.5%;经第2次巢式PCR测定。另6例全部检出SRY基因扩增片段,累计检出率为100%,妊娠女性胎儿的8例孕妇血浆中,均未检出SRY基因扩增片段,4例X性连锁遗传病家族史者均检出SRY基因扩增片段。结论 从孕妇血浆中提取胎儿游离DNA行胎儿性别诊断是一种快速,简便,准确的产前诊断方法。     

First-trimester fetal sex determination in maternal serum using real-time PCR.

Fetal sex prediction can be achieved using PCR targeted at the SRY gene by analysing cell-free fetal DNA in maternal serum. Unfortunately, the results reported to date show a lack of sensitivity, especially during the first trimester of pregnancy. Therefore, determination of fetal sex by maternal serum analysis could not replace karyotype analysis following chorionic villus sampling. A new highly sensitive real-time PCR was developed to detect an SRY gene sequence in maternal serum. Analysis was performed on 121 pregnant women during the first trimester of pregnancy (mean gestational age: 11.8 weeks). Among them, 51 had at least one previous male-bearing pregnancy. Results were compared with fetal sex. SRY PCR analysis of maternal serum was in complete concordance with fetal sex. Among the 121 pregnant women, 61 were bearing a male fetus and 60 a female fetus. No false-negative results were observed. Furthermore, no false-positive results occurred, even though 27 women carrying a female fetus during the current pregnancy had at least one previous male-bearing pregnancy. This study demonstrates that a reliable, non-invasive sex determination can be achieved by PCR analysis of maternal serum during the first trimester of pregnancy. This non-invasive approach for fetal sex prediction should have great implications in the management of pregnant women who are carriers of an X-linked genetic disorder. Prenatal diagnosis might thus be performed for male fetuses only, avoiding invasive procedures and the risk of the loss of female fetuses.     

9例多胎妊娠合并胎儿染色体异常患者的产前诊断和治疗

目的探讨多胎妊娠合并胎儿染色体异常的产前诊断方法及选择性减胎术定位方法。 方法选取2012年1月至2013年12月就诊于广州医科大学附属第三医院9例多胎妊娠合并胎儿染色体异常患者的临床资料,采用回顾性研究方法对其产前诊断方法、染色体异常情况、选择性减胎术的方法及妊娠结局进行分析。 结果9例患者中3例为三胎妊娠,6例为双胎妊娠。(1)产前诊断：①超声检查：9例患者早孕期行超声检查,均提示存在胎儿颈项透明层(nuchal translucency, NT)增厚,孕中期超声检查提示有6例患者存在胎儿结构异常,包括颈部囊肿、心脏异常、外生殖器畸形、足内翻、全身水肿等;②染色体检查：5例胎儿21-三体综合征,1例Turner综合征,1例染色体微缺失,1例染色体重复,1例双胎染色体异常。(2)治疗及妊娠结局：9例患者中7例患者行选择性减胎术治疗,1例流产,3例早产(新生儿均存在并发症),3例足月分娩(新生儿均未见异常);2例患者拒绝减胎,1例于孕中期自然流产,1例于孕35^＋周剖宫产分娩(1胎儿为21-三体综合征,另一胎儿为健康儿)。 结论多胎妊娠应注重早孕期染色体筛查,确诊宫内胎儿染色体异常的患者可在超声引导下行选择性减胎术治疗。     

Relative risk of abnormal karyotype in fetuses found to have an atrioventricular septal defect (AVSD) on fetal echocardiography

One hundred and twenty-five fetuses were identified as having an AVSD with normal venous connections, normal arterial connections and normal cardiac situs on fetal echocardiography. Fetal karyotype was known in 111 of these cases. The relative risk of fetal trisomy 21 at mid-trimester was 107 (95% CI 87-127) times the expected number of cases compared with risk from maternal age alone, and that for trisomy 21,18 or 13 was 95 (95% CI 79-109). This data may be useful in counselling pregnant women about risk of fetal karyotypic abnormality after a diagnosis of fetal AVSD.     

Rapid karyotyping in fetuses with abnormal sonogram

Prenatal karyotyping of fetuses having an abnormal sonogram was undertaken in 27 pregnancies between 17 and 39 weeks, using fetal blood obtained by percutaneous umbilical cord blood sampling under ultrasound guidance. Eight chromosomal abnormalities (29.7%) were detected, including 45, X (2 cases), trisomy 21(1 case), 46, XY,-13,+t(13,13) (1 case), 47, XX,+18(3 cases), 47, XXY (1 case). Nineteen fetuses had a normal karyotype (46,XX:9 cases, 46,XY:10 cases). The fetal karyotype was available within 72 h and fetal management was planned accordingly. We concluded that in fetuses with an abnormal sonogram, rapid karyotyping using fetal blood obtained under ultrasound guidance had important implications in obstetric and neonatal management and would facilitate genetic counselling.     

Pregnancy outcome in fetuses with increased nuchal translucency and normal karyotype

OBJECTIVE: This study was conducted to evaluate pregnancy outcome and mid- and long-term prognosis of cases with nuchal translucency > or =4 mm and normal karyotype. METHODS: Retrospective analysis of 160 cases who presented with a nuchal translucency > or =4 mm when the CRL was between 45 and 84 mm was undertaken. Cystic hygromas were excluded. When the karyotype was normal a detailed anomaly scan was performed at 20 to 24 weeks followed by serial ultrasound examination. Clinical examination of the neonates was performed by a paediatrician. Long-term follow-up was completed through a questionnaire filled in by parents, GPs and paediatricians. RESULTS: 160 fetuses had an NT > or =4 mm. 44.3% had an abnormal karyotype. Of the 55.7% with normal karyotypes, 74 % did not show any abnormalities on follow-up ultrasound scan. Mid- and long-term outcome was known in 91% of the cases. 6.4% had a malformation diagnosed only at birth. Among the normal neonates, 11.1% are considered to have a significant neurological handicap or orthopaedic problems at 12 to 72 months of age. CONCLUSION: In an unselected population, NT > or =4 mm is associated with a high incidence of chromosomal and non chromosomal abnormalities. Even when the fetal karyotype and serial ultrasound examinations are considered to be normal, the risk of fetal malformation and developmental delay should not be underestimated.     

Fetal blood chromosome analysis: some new indications for prenatal karyotyping

Prenatal karyotyping using stimulated fetal blood lymphocytes was undertaken in 170 pregnancies between 16 and 36 weeks gestation for the following reasons--mosaicism or marker chromosomes found in amniotic fluid culture; a family history of X-linked mental retardation with fragile Xq28; fetal abnormalities detected ultrasonographically; late booking or amniotic fluid culture failure in patients with advanced age or balanced translocations; and twin pregnancies discordant for a chromosomal anomaly. Forty-one karyotypic abnormalities were detected (24%). These were: 45,X (7 cases), trisomy 13 (5 cases), trisomy 18 (6 cases), trisomy 21 (4 cases), twin pregnancy where one twin had trisomy 21 (1 case), supernumerary marker chromosome (3 cases, one of which occurred in a twin pregnancy), triploidy (3 cases), X-linked mental retardation with fragile site at Xq28 in males (6 cases), fetal erythroleukaemia (3 cases including 2 cases with Turner's), Fanconi's anaemia (1 case), unbalanced chromosome translocation 47,XY+der22,t(11;22) mat (1 case), mos 46,XX18p-/46,XX,-18+i(18q) (1 case), 46,XXdel(2q) (1 case), and 46,XYt(5;17) de novo (1 case). In fetuses at high risk of a chromosome aberration, a rapidly obtained karyotype is helpful and fetoscopy and fetal blood sampling are justified in the second or third trimester.