Prenatal and postnatal prevalence of Turner's syndrome: a registry study.

OBJECTIVE--To study prevalence of Turner''s syndrome in Denmark and to assess validity of prenatal diagnosis. DESIGN--Study of data on prenatal and postnatal Turner''s syndrome in Danish Cytogenetic Central Register. SUBJECTS--All registered Turner''s syndrome karyotypes (100 prenatal cases and 215 postnatal cases) during 1970-93. MAIN OUTCOME MEASURES--Prevalence of Turner''s syndrome karyotypes among prenatally tested fetuses and Turner''s syndrome among liveborn infants. RESULTS--Among infant girls, prevalence of Turner''s syndrome was 32/100,000. Among female fetuses tested by amniocentesis, prevalence of Turner''s syndrome karyotypes was 176/100,000 (relative risk of syndrome, 6.74 compared with prevalence among untested pregnancies). Among female fetuses tested by chorion villus sampling, prevalence of syndrome karyotypes was 392/100,000 (relative risk, 16.8). We excluded prenatal tests referred because of results of ultrasound scanning: among fetuses tested by amniocentesis revised relative risk was 5.68, while revised relative risk among fetuses tested by chorion villus sampling was 13.3. For 29 fetuses with prenatal diagnosis of possible Turner''s syndrome, pregnancy was allowed to continue and 24 children were live born. Thirteen of these children were karyotyped postnatally, and diagnosis of Turner''s syndrome had to be revised for eight, seven being normal girls and one boy. This gives tentative predictive value of amniocentesis in diagnosing Turner''s syndrome of between 21% and 67%. There was no significant relation between mother''s age and risk of Turner''s syndrome. CONCLUSIONS--Discrepancy between prenatal and postnatal prevalence of Turner''s syndrome challenges specificity of prenatal examination in diagnosing Turner''s syndrome.     

Ethical issues in amniocentesis and abortion

The ethical issues surrounding amniocentesis are seen as centering on 4 focal points. First is the policy of the diagnostic treatment center. Here, 2 questions arise: Is the client involved in a high-risk pregnancy? And, if a positive diagnosis is made, will the parents consent to an abortion? Second is the role of the genetic counselor, which is seen as supportive rather than leading. He should assist the prospective parents in reaching a decision to undergo amniocentesis and possible abortion that is mutually acceptable. The prospective parents, the third focal point, may face the question of deciding what is normal. The clients must also realize the terrible strains that are put on a marriage into which a severely defective child has been born. The fourth focal point is public policy. While amniocentesis may appear to threaten some values held important in our society, the author regards the procedure as an interim solution on the road to an understanding of and ability to treat genetic defects.     

Prenatal diagnosis of genetic disease in Canada: report of a collaborative study.

A study of 1223 amniocenteses carried out during 1020 pregnancies in 990 women showed that 2nd-trimester amniocentesis at about 16 weeks'' gestation is a safe, accurate and reliable procedure for the diagnosis of certain classes of genetic disease when it is monitored by ultrasound, performed by a trained obstetrician and carried out in a major health sciences centre. The percentage of fetal losses (4.7%) and neonatal deaths (0.5%) during the study was not greater than in control samples for women 35 years of age and older. The best results were obtained when needles of gauge 20 or 21 were used. The use of needles of gauge 19 or larger and more than two insertions during a single amniocentesis were associated with a significantly greater frequency of fetal loss than a second or even a third amniocentesis during the same pregnancy. For 39 fetuses (3.8%) a diagnosis of a genetic abnormality was made and 23 male fetuses were found to be potentially hemizygous for an X-linked gene. There were 51 therapeutic abortions as a result of the diagnosis. Sixty-six tests (5.4%) gave an inconclusive result and seven (0.6%) gave an erroneous diagnosis; five of the latter (two false-positives and three false-negatives) resulted from the alpha1-fetoprotein test for neural-tube defects and in two cases the sex was incorrectly determined. The frequency of all chromosome abnormalities was 1:20 when the mother''s age was 40 years or more and 1:60 when the mother''s age was between 35 and 39 years. When a mother had previously had a child with a chromosome abnormality the risk of recurrence of such an abnormality was 1:100 when the age of the mother was 35 years or more.     

Prenatal Diagnosis and Genetic Counseling

Since the early 1960''s knowledge regarding human genetics has increased at an exponential rate. Because genetics was not commonly taught in medical schools before the late 1960''s, this review article is intended to acquaint physicians or refresh their knowledge regarding chromosomal, mendelian and multifactorial inheritance and the indications for prenatal diagnosis. Establishing an accurate diagnosis and mode of inheritance is essential in identifying and selecting those families at risk for genetic disease in their offspring. Medical genetics is evolving as a specialty in order to provide consultation and, if needed, management of those families who would benefit by genetic services. Families who would benefit from genetic counseling include, for example, those in whom any of the following conditions is present: known chromosomal disorders, known disorders due to mendelian inheritance, mental retardation of unknown origin, failure of sexual maturation or failure of sexual development, congenital malformations, floppy infant syndrome or leukemia.A list of more than 70 disorders now detectable in a fetus by means of amniocentesis provides a beginning in the prevention of genetic disease. Knowledge regarding these diseases allows a physician to provide families with accurate risk figures so that they may make informed decisions about having children. Also, a compassionate and nonjudgmental approach to counseling is essential. Decisions, in the final analysis, must be made by the family but aided and supported by the physician.     

Appraisal of a new scheme for prenatal screening for Down's syndrome.

OBJECTIVE--To appraise a new method of prenatal screening for Down''s syndrome based on maternal serum concentrations of alpha fetoprotein, unconjugated oestriol, and human chorionic gonadotrophin combined with maternal age--the "triple test." DESIGN--Examination of the cost effectiveness of the triple test relative to screening only by maternal age over a range of population detection rates. SETTING--Leicestershire Health Authority. MAIN OUTCOME MEASURES--Costs per affected fetus detected. RESULTS--The triple test is more cost effective than screening only by maternal age for risk cut off points for amniocentesis, resulting in a detection rate over 45%. The most efficient detection rate is around 60-65%, for which the cost per case detected is around 29,000 pounds, through screening with higher detection rates is still likely to be cost beneficial. CONCLUSIONS--Prenatal screening for Down''s syndrome based on the triple test should replace screening based only on maternal age. Individual women''s preferences should be elicited by the use of structured decision analysis in order to maximise utility and so increase the benefits of the screening programme.     

颈项透明层厚度超声联合无创DNA对孕妇胎儿染色体非整倍体异常诊断效能的影响

摘要 目的：探讨颈项透明层(nuchal translucency,NT)厚度超声联合无创DNA对孕妇胎儿染色体非整倍体异常诊断效能的影响。方法：2018年7月到2020年4月选择在本院进行产前筛查的孕妇120例,所有孕妇都给予NT厚度超声联合无创DNA检查,采用羊水穿刺分析检测结果为阳性的胎儿情况。结果：120例胎儿的NT厚度为0.8~10 mm,平均厚度为1.57±0.41 mm;不同孕妇年龄的NT厚度对比差异无统计学意义(P>0.05)。以羊水穿刺检测结果为金标准,120例胎儿中检出染色体非整倍体异常7例,NT超声检出12例,无创DNA检出13例,联合检出14例。NT超声、无创DNA与联合诊断的染色体非整倍体异常敏感性为57.1%、85.7%和100.0%,特异性为92.9%、93.8%和93.8%。检测结果为阳性的14例胎儿中,还包括3例淋巴水囊瘤,2例单脐动脉伴胎儿宫内发育迟缓,1例胎儿双肾畸形,1例胎儿并腿畸形。结论：颈项透明层厚度超声联合无创DNA在孕妇胎儿染色体非整倍体异常中的诊断具有操作简便、无创伤等特点,诊断敏感性与特异性都比较高,可对临床医生遗传咨询有一定的参考价值。     

Prenatal diagnosis of hemoglobinopathies: evaluation of techniques for analysing globin-chain synthesis in blood samples obtained by fetoscopy.

Three techniques for analysing hemoglobin synthesis in blood samples obtained by fetoscopy were evaluated. Of the fetuses studied, 12 were not at risk of genetic disorders, 10 were at risk of beta-thalassemia, 2 were at risk of sickle cell anemia and 1 was at risk of both diseases. The conventional method of prenatal diagnosis of hemoglobinopathies, involving the separation of globin chains labelled with a radioactive isotope on carboxymethyl cellulose (CMC) columns, was compared with a method involving globin-chain separation by high-pressure liquid chromatography (HPLC) and with direct analysis of labelled hemoglobin tetramers obtained from cell lysates by chromatography on ion-exchange columns. The last method is technically the simplest and can be used for diagnosing beta-thalassemia and sickle cell anemia. However, it gives spuriously high levels of adult hemoglobin in samples containing nonlabelled adult hemoglobin. HPLC is the fastest method for prenatal diagnosis of beta-thalassemia and may prove as reliable as the CMC method. Of the 13 fetuses at risk for hemoglobinopathies, 1 was predicted to be affected, and the diagnosis was confirmed in the abortus. Of 12 predicted to be unaffected, 1 was aborted spontaneously and was unavailable for confirmatory studies, as were 3 of the infants; however, the diagnosis was confirmed in seven cases and is awaiting confirmation when the infant in 6 months old in one case. Couples at risk of bearing a child with a hemoglobinopathy should be referred for genetic counselling before pregnancy or, at the latest, by the 12th week of gestation so that prenatal diagnosis can be attempted by amniocentesis, safer procedure, with restriction endonuclease analysis of the amniotic fluid cells.     

Amniotic fluid zinc in risk pregnancies

The zinc concentration of amniotic fluid (AF) of 129 pregnant women was analyzed by the flame atomic absorption spectrometry. This prospective study was performed in order to find out whether the determination of the AF zinc concentration can be used to monitor the growth and development of the fetus. There were two groups of patients: early stage (15th–19th gestation wk) in which the amniocentesis was performed as a prenatal genetic examination, and late stage (26th–40th wk) in which the amniocentesis was performed due to obstetric reasons. The average AF zinc concentrations were 1.2 and 1.0 μmol/L in the early and late gestation group, respectively. The AF zinc concentration did not correlate with the weight, height, or Apgar scores of the newborn nor with the maternal diseases, age, or parity. The AF zinc concentration in the late gestation group was significantly lower if the fetus was male than if it was female. If the AF was greenish the zinc concentration was elevated. One malformation, congenital nephrosis, with an exceptionally high zinc concentration (9.0 μmol/L), was found.     

Screening for Down's syndrome in the North East Thames region.

The suggested strategies for a screening programme for Down''s syndrome by maternal serum alpha fetoprotein concentration were examined and tested on the experience of the North East Thames Regional. Screening by maternal serum alpha fetoprotein concentration may be used to identify pregnancies at increased risk, but this is useful only in women aged over 32 whose collective risk is greater than one in 200. The absolute probability of carrying babies with Down''s syndrome for individuals in this high risk group can then be calculated and used to decide whether further diagnosis by amniocentesis is desired.     

Prenatal diagnosis--principles of diagnostic procedures and genetic counseling

The frequency of inherited malformations as well as genetic disorders in newborns account for around 3-5%. These frequency is much higher in early stages of pregnancy, because serious malformations and genetic disorders usually lead to spontaneous abortion. Prenatal diagnosis allowed identification of malformations and/or some genetic syndromes in fetuses during the first trimester of pregnancy. Thereafter, taking into account the severity of the disorders the decision should be taken in regard of subsequent course of the pregnancy taking into account a possibilities of treatment, parent's acceptation of a handicapped child but also, in some cases the possibility of termination of the pregnancy. In prenatal testing, both screening and diagnostic procedures are included. Screening procedures such as first and second trimester biochemical and/or ultrasound screening, first trimester combined ultrasound/biochemical screening and integrated screening should be widely offered to pregnant women. However, interpretation of screening results requires awareness of both sensitivity and predictive value of these procedures. In prenatal diagnosis ultrasound/MRI searching as well as genetic procedures are offered to pregnant women. A variety of approaches for genetic prenatal analyses are now available, including preimplantation diagnosis, chorion villi sampling, amniocentesis, fetal blood sampling as well as promising experimental procedures (e.g. fetal cell and DNA isolation from maternal blood). An incredible progress in genetic methods opened new possibilities for valuable genetic diagnosis. Although karyotyping is widely accepted as golden standard, the discussion is ongoing throughout Europe concerning shifting to new genetic techniques which allow obtaining rapid results in prenatal diagnosis of aneuploidy (e.g. RAPID-FISH, MLPA, quantitative PCR).     

Prenatal diagnosis of chromosome disorders in Tunisian population

Cytogenetic prenatal diagnosis (PND) is under national health program in most developed countries, while it concerns a small part of population at risk in developing countries. Finance is common reason of absence of PND development, but socio-cultural believes play an important role in Arab Muslim countries. In this paper we report results of 3110 fetal karyotypes carried out in a Tunisian population, by cultured amniocytes analysis. It is the largest report in a Muslim Arab country in our Knowledge. Abnormal karyotypes rate was 4.18% classified in two groups: bad prognosis (3.05%) and good prognosis (1.13%). Common amniocentesis indication was maternal age. The highest predictive value was observed in balanced karyotype and fetal ultrasound findings indications. Maternal serum markers were not commonly used for trisomy 21 screening. Pregnancy termination that is permitted by legal and religious authorities was accepted by 94,74% parents. Information about PND outcomes was given by genetic counselling prior to fetal sampling, pregnancy interruption was discussed with parents at cytogenetic result announcement. The authors conclude that in order to prevent mental and physical handicap related to cytogenetic disorders we have to promote PND by education for population, genetic counselling and fetal ultrasound screening; all three methods available in Tunisia.     

Haplotype-based approach for noninvasive prenatal diagnosis of congenital adrenal hyperplasia by maternal plasma DNA sequencing

Prenatal diagnosis of congenital adrenal hyperplasia (CAH) is of clinical significance because in utero treatment is available to prevent virilization of an affected female fetus. However, traditional prenatal diagnosis of CAH relies on genetic testing of fetal genomic DNA obtained using amniocentesis or chorionic villus sampling, which is associated with an increased risk of miscarriage. The aim of this study was to demonstrate the feasibility of a new haplotype-based approach for the noninvasive prenatal testing of CAH due to 21-hydroxylase deficiency. Parental haplotypes were constructed using target-region sequencing data of the parents and the proband. With the assistance of the parental haplotypes, we recovered fetal haplotypes using a hidden Markov model (HMM) through maternal plasma DNA sequencing. In the genomic region around the CYP21A2 gene, the fetus inherited the paternal haplotype ‘0’ alleles linked to the mutant CYP21A2 gene, but the maternal haplotype ‘1’ alleles linked to the wild-type gene. The fetus was predicted to be an unaffected carrier of CAH, which was confirmed by genetic analysis of fetal genomic DNA from amniotic fluid cells. This method was further validated by comparing the inferred SNP genotypes with the direct sequencing data of fetal genomic DNA. The result showed an accuracy of 96.41% for the inferred maternal alleles and an accuracy of 97.81% for the inferred paternal alleles. The haplotype-based approach is feasible for noninvasive prenatal testing of CAH.     

A benefit‐cost analysis of amniocentesis

Abstract

This study applies benefit‐cost analysis to one area of prenatal diagnosis— amniocentesis. The ultimate purpose of such a study is to provide useful guidelines to policy makers. An attempt is made to exhaustively list benefits and costs, whether measurable or not. Those which can be quantified are estimated. On the basis of these benefit‐cost estimates, the study concludes that a program of amniocentesis for all pregnant women beyond age 32 would be warranted. This economic analysis, however, is only one aspect of a policy decision. Moral, legal, and ethical questions must also be considered.     

Chromosome Analysis before Birth and its Value in Genetic Counselling

Chromosome analysis of amniotic cell cultures was achieved in 29 out of 30 consecutive patients who were referred for genetic counselling during pregnancy. Amniocentesis was performed without any apparent untoward maternal or fetal complication. The only pregnancy terminated was that of a carrier of X-linked granulomatous disease, in whom the amniotic cells showed that the fetus was male and also had Down''s syndrome (trisomy G). Chromosome analysis in the remaining 28 patients showed normal karyotypes. The interval between amniocentesis and a definitive karyotype varied from 7 to 31 (average 18·4) days.The reliability of chromosome analysis from amniotic cell culture and of fetal sex determination by means of the sex chromatin and Y-fluorescence techniques was studied further in amniotic fluid from cases of therapeutic abortion and of rhesus incompatibility. The fetal sex was correctly determined in all cases. It is concluded that antenatal diagnosis of genetic disease by amniocentesis now permits a more practical approach to genetic counselling.     

The use of cloned Y chromosome-specific DNA probes for fetal sex determination in first trimester prenatal diagnosis

Summary Prenatal diagnosis by chorion biopsy in the first trimester of pregnancy has advantages over second trimester amniocentesis because diagnosis can be achieved at 9–12 weeks gestation, reducing prenatal anxiety and avoiding the trauma of late abortion. DNA can be prepared from chorionic villus biopsies in sufficient quantity and purity for use in prenatal diagnosis systems using specific DNA probes hybridised to restriction endonuclease digests.DNA probes derived from the Y chromosome have been used to determine fetal sex. The use of such probes means that the chromosomal sex of the fetus can be identified more quickly than by chromosome preparation and more accurately than by sex chromatin staining, and has the additional advantage that the same DNA preparation can be used for other diagnostic tests. A dot hybridisation method has been successfully used to provide even more rapid results than conventional hybridisation to Southern blots of restriction endonuclease digests.There is a risk that Y chromosome-specific DNA probes for sex determination may be subject to error if the parents have extreme Y chromosome variants such as a small or non-fluorescent Y or a Y autosome chromosome translocation. The precise extent to which such chromosome variants may lead to error has been investigated. Even extreme Y chromosome variants totally lacking fluorescence were identified as male by the cloned probes used. However, Y autosome translocations carried by females could cause error if not identified in the parents. The value of the probes has been confirmed provided that parental chromosomes and DNA are examined in parallel with the chorionic biopsy material     

Health-related quality-of-life assessment of prenatal diagnosis: chorionic villi sampling and amniocentesis

This study assesses the health-related quality-of-life (HRQL) effects of chorionic villi sampling (CVS) and genetic amniocentesis (GA), including both process and outcomes of prenatal diagnosis. The HRQL of 126 women participating in a randomized controlled clinical trial of CVS versus GA in Toronto and Hamilton, Ontario, was assessed in four interviews at weeks 8, 13, 18, and 22 of pregnancy. Statistical analyses included analysis of variance, repeated measures analysis of covariance, chi-square, Fisher's exact test, Student's t-tests, and paired t-tests. Utility scores for patients undergoing CVS exceeded those for GA patients at week 18 (p = 0.04). Utility scores for hypothetical health states did not differ significantly by trial arm. CVS results in slightly improved HRQL during prenatal diagnosis. This advantage needs to be weighed against the high disutility patients attach to infrequent outcomes associated with pregnancy losses, equivocal diagnoses, and diagnostic inaccuracy.     

Proteomic determination of metabolic enzymes of the amnion cell: Basis for a possible diagnostic tool?

Amniocentesis is a valuable and standard procedure for prenatal diagnosis of genetic or inborn errors of metabolism. Amnion cells are cultivated and chromosomes or proteins can be examined to provide molecular diagnosis. Mainly individual proteins are searched for based upon pedigrees and/or anamnesis. As inborn errors of metabolism involve a vast diversity of metabolic enzymes, we aimed to find a screening method for a large series of metabolic enzymes. Amnion cells were obtained from amniocentesis and subjected to proteomic analysis. We used two-dimensional gel electrophoresis with in-gel digestion followed by matrix-assisted laser desorption/ionization-time of flight analysis, to identify metabolic enzymes. Furthermore, we compared metabolic proteins in amnion cells from controls with those from Down Syndrome (DS). Enzymes involved in carbohydrate handling, amino acid handling, -purine metabolism and intermediary metabolism as well as miscellaneous metabolic pathways were detected. Protein levels of several enzymes were significantly deranged in samples obtained from patients with DS. This approach, with the advantage of the concomitant determination of many enzyme proteins, may form the basis for future metabolic screens when amniocentesis is carried out.     

Lethal osteogenesis imperfecta congenita and a 300 base pair gene deletion for an alpha 1(I)-like collagen.

Broad boned lethal osteogenesis imperfecta is a severely crippling disease of unknown cause. By means of recombinant DNA technology a 300 base pair deletion in an alpha 1(I)-like collagen gene was detected in six patients and four complete parent-child groups including patients with this disease. One from each set of the patients'' clinically unaffected parents also carried the deletion, implying that affected patients were genetic compounds. The study suggests that prenatal diagnosis should be possible with 100% accuracy in subjects without the deletion and with 50% accuracy in those who possess it (who would be either heterozygous--normal, or affected with the disease).     

Periodic health examination, 1996 update: 1. Prenatal screening for and diagnosis of Down syndrome. Canadian Task Force on the Periodic Health Examination.

OBJECTIVE: To make recommendations to physicians providing prenatal care on (1) whether prenatal screening for and diagnosis of Down syndrome (DS) is advisable and (2) alternative screening and diagnosis manoeuvres. OPTIONS: "Triple-marker" screening of maternal serum levels of alpha-fetoprotein, human chorionic gonadotropin and unconjugated estriol; fetal ultrasonographic examination; amniocentesis; and chorionic villus sampling (CVS). OUTCOMES: Accuracy of detection of DS in fetuses, and risks to the mother, including psychologic distress, and to the fetus from the screening and diagnostic interventions. EVIDENCE: A MEDLINE search for relevant articles published from Jan. 1, 1966, to Mar. 31, 1994, with the use of MeSH terms "Down syndrome," "prenatal diagnosis," "screening," "prevention," "amniocentesis," "chorionic villus sampling," "ultrasonography," "anxiety," "depression" and "psychological stress" and a manual search of bibliographies, recent issues of key journals and Current Contents. VALUES: The evidence-based methods and values of the Canadian Task Force on the Periodic Health Examination were used. A high value was placed on providing pregnant women with the opportunity to determine whether they are carrying a fetus with DS and to make choices concerning the termination of the pregnancy. The economic issues involved are complex and were not considered. BENEFITS, HARMS AND COSTS: Triple-marker screening identifies an estimated 58% of fetuses with DS, but it has an estimated rate of true-positive results of 0.1% and of false-positive results of 3.7% (given a risk cut-off of one chance in 190 of DS). These rates vary with maternal age and the risk cut-off chosen. Women with a known risk of having a fetus with DS (e.g., those who have had a previous child with DS) may benefit from a reduction in anxiety after confirmation that their fetus does not have DS. Screening allows women at low risk of having a child with DS to detect fetuses with the syndrome, but may cause psychologic distress if there is a false-positive screening test result. Up to 20% of women with positive results of screening tests may decline to undergo a subsequent amniocentesis. Amniocentesis and CVS are very accurate in diagnosing DS in fetuses and have a very low rate of serious complications for the mother. Amniocentesis is associated with a 1.7% rate of fetal loss when it is performed after 16 weeks'' gestation, whereas the rate among controls is 0.7% (for a difference of 1%, 95% confidence interval 0.3% to 1.5%). CVS entails a greater risk of fetal loss than amniocentesis (odds ratio 1.32, 95% confidence interval 1.11 to 1.57). There is little evidence from controlled trials of significant associations between amniocentesis or CVS and neonatal morbidity or malformations; however, samples have been too small to show differences in rare outcomes. Results from some case-control studies suggest that CVS increases the risk of transverse limb deficiency. Costs were not considered because they are beyond the scope of this review. RECOMMENDATIONS: There is fair evidence to offer triple-marker screening through a comprehensive program to pregnant women under 35 years of age (grade B recommendation). Women given detailed information about serum-marker screening show more satisfaction with the screening than those not given this information. There is fair evidence to offer amniocentesis or CVS to pregnant women 35 years of age and older and to women with a history of a fetus with DS or of a chromosome 21 anomaly (grade B recommendation). Information on the limitations and advantages of each procedure should be offered. Triple-marker screening may be offered as an alternative to CVS or amniocentesis to pregnant women over 35. VALIDATION: Recommendations concerning prenatal diagnosis are similar to those of the US Preventive Services Task Force, the Society of Obstetricians and Gynaecologists of Canada, the Canadian College of Medical Geneticists and the Cochrane Pregnancy and Childbirth Group. No previous specific recommendations concerning triple-maker screening exist. SPONSORS: These guidelines were developed and endorsed by the Canadian Task Force on the Periodic Health Examination, which is funded by Health Canada and the National Health Research and Development Program.