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PubMed2006

If nuchal translucency screening is combined with first-trimester serum screening the need for fetal karyotyping decreases.

BACKGROUND: This case-control study was performed to evaluate whether adding first-trimester maternal serum testing to nuchal translucency measurement would improve the antenatal detection of Down's syndrome and decrease the number of women offered fetal karyotyping. METHODS: In the Swedish Nuchal Translucency Trial (the NUPP trial), 39,572 pregnant women were randomized to a routine scan at 12-14 gestational weeks including nuchal translucency screening for Down's syndrome, or a routine scan at 16-18 gestational weeks. From the early scan group 47 pregnancies with Down's syndrome were identified and for each case three controls were chosen. Of the 189 women asked to participate, 31 cases and 108 controls with a singleton pregnancy and frozen serum from 8-14 gestational weeks available for analysis accepted participation. Maternal sera were analyzed for free beta human chorionic gonadotrophin and pregnancy-associated plasma protein A. The risk for Down's syndrome was calculated using combinations of maternal age, crown-rump length, nuchal translucency, and biochemistry. A risk > or =1/250 was considered increased and an indication for fetal karyotyping. RESULTS: Risk calculated on the basis of maternal age alone would have identified 21 of the 31 Down's syndrome cases by karyotyping 61 of the 139 fetuses. Maternal age and nuchal translucency would have identified 29 cases by karyotyping 51 fetuses. Maternal age, nuchal translucency, and biochemistry would also have identified 29 cases by karyotyping 37 fetuses. CONCLUSIONS: By adding first trimester biochemistry to nuchal translucency measurement the detection rate of fetuses with Down's syndrome seems to remain unchanged whereas the antenatal risk group to be offered fetal karyotyping decreases.

Adult↗
PubMed1991

Prenatal diagnosis of alpha- and beta-thalassaemias in Singapore--current status.

Prenatal diagnosis was performed in 31 pregnancies where the fetuses were at risk for either homozygous alpha(0) - or beta-thalassaemia. First-trimester prenatal diagnosis by DNA analysis using chorionic villi was carried out for 17 pregnancies at risk for homozygous alpha (0)-thalassaemia. The alpha-globin genes in fetal DNA were detected by gene mapping using restriction endonuclease mapping and hybridization with cloned alpha-globin probe. Homozygous alpha (0)-thalassaemia was detected in four fetuses and the results were subsequently confirmed by electrophoresis of the cord blood where only Hb Barts was detected. Prenatal diagnosis for beta-thalassaemia was carried out by globin chain biosynthesis using fetal blood at 18-20 weeks' gestation. Using carboxymethyl (CM) sepharose chromatography, homozygous beta-thalassaemia was predicted in six pregnancies, and one fetus carried Hb E-beta thalassaemia. The seven pregnancies were terminated and globin chain analysis using cord blood confirmed the prenatal diagnoses. The remaining seven fetuses were diagnosed as either normal or beta-thalassaemia carriers. Using DNA analysis and globin chain biosynthesis for prenatal diagnosis of homozygous alpha(0)- and beta-thalassaemia, a 100% correlation was achieved with fetuses predicted to possess the homozygous condition.

Chorionic Villi Sampling↗
PubMed2006

Prenatal diagnosis of beta-thalassemia by reverse dot-blot hybridization in southern China.

Beta-thalassemia (thal) is the most common genetic disease and is widely distributed in southern China. Prenatal diagnosis is needed to prevent the birth of thalassemic offspring in couples at-risk. This can be performed in the first or second trimester of pregnancy by DNA analysis using polymerase chain reaction (PCR). As there are more than 30 mutations causing beta-thal in Chinese, the point mutation detection by reverse dot-blot for common mutations together with direct DNA sequencing was developed for prenatal diagnosis. Using reverse dot-blot, we were able to offer complete diagnosis in 315 (99.4%) of 317 pregnancies. Only two fetuses needed the DNA sequencing technique for diagnosis. Of the 319 at-risk fetuses, 82 (25.7%) were found to be normal, 143 (44.8%) to be heterozygous for beta-thal and 94 (29.5%) to be affected with beta-thal. Therefore, the combination of reverse dot-blot with direct DNA sequencing can perform prenatal diagnosis by DNA analysis in almost all cases at- risk of beta-thal in southern China.

China↗
PubMedDate not supplied

Prenatal diagnosis in congenital contractural arachnodactyly.

Congenital contractural arachnodactyly (CCA) is a heritable connective tissue disorder caused by defects in the gene encoding fibrillin-2 (FBN2). People with CCA typically have a marfanoid habitus, flexion contractures, severe kyphoscoliosis, abnormal pinnae, and muscular hypoplasia. Because of the relative infrequency of the syndrome and its generally mild to moderate severity, prenatal diagnosis had not previously been sought. Here we report prenatal diagnosis in a family with CCA. Because the course of the disease in the proband was rather severe, she had requested genetic counseling as early as age 17. She delayed childbearing until prenatal diagnosis for CCA became possible. This decision was supported by her mother and later her husband. Because she shared the same genotype with her husband, genetic linkage analysis of this family did not alter the a priori 50% risk of having an affected child. The possibility of unambiguously ascertaining the affected status of a fetus homozygous for the tested FBN2 marker was sufficient for the family to pursue prenatal diagnosis. This case strongly points to the importance of informed decisions now that genetic testing is becoming commonplace.

Adult↗
PubMed1998

A simple VNTR-PCR method for detecting maternal cell contamination in prenatal diagnosis.

The effectiveness of variable number tandem repeats (VNTRs) was evaluated in the detection of maternal cell contamination. Nonradioactive PCRs were performed on 30 sets of prenatal tissue using VNTRs as primers. The combination of two VNTRs (YNZ22 and APOB) provided information on all 30 cases, distinguishing maternal-fetal genotype patterns and detecting maternal cell contamination in 5 of 30 prenatal cases. The amplification of these two VNTRs does not require radioactive or fluorescence labeling, and a small gel electrophoresis is sufficient to see the maternal-fetal genotype pattern. By this method, detection of maternal cell contamination in prenatal tissues can be obtained in 1 day, without the use of expensive instruments, thus providing DNA laboratories a very sensitive, rapid, and simple proof pretest on all prenatal tissues before performing the final genetic diagnostic testing.

Amniocentesis↗
PubMed2001

Prenatal screening and genetics.

Although the term 'genetic screening' has been used for decades, this paper discusses how, in its most precise meaning, genetic screening has not yet been widely introduced. 'Prenatal screening' is often confused with 'genetic screening'. As we show, these terms have different meanings, and we examine definitions of the relevant concepts in order to illustrate this point. The concepts are i) prenatal, ii) genetic screening, iii) screening, scanning and testing, iv) maternal and foetal tests, v) test techniques and vi) genetic conditions. So far, prenatal screening has little connection with precisely defined genetics. There are benefits but also disadvantages in overstating current links between them in the term genetic screening. Policy making and professional and public understandings about screening could be clarified if the distinct meanings of prenatal screening and genetic screening were more precisely observed.

Amniocentesis↗
PubMed1992

DNA methylation represses FMR-1 transcription in fragile X syndrome.

Fragile X syndrome is the most frequent form of inherited mental retardation and segregates as an X-linked dominant with reduced penetrance. Recently, we have identified the FMR-1 gene at the fragile X locus. Two molecular differences of the FMR-1 gene have been found in fragile X patients: a size increase of an FMR-1 exon containing a CGG repeat and abnormal methylation of a CpG island 250 bp proximal to this repeat. Penetrant fragile X males who exhibit these changes typically show repression of FMR-1 transcription and the presumptive absence of FMR-1 protein is believed to contribute to the fragile X phenotype. It is unclear, however, if either or both molecular differences in FMR-1 gene is responsible for transcriptional silencing. We report here the prenatal diagnosis of a male fetus with fragile X syndrome by utilizing these molecular differences and show that while the expanded CGG-repeat mutation is observed in both the chorionic villi and fetus, the methylation of the CpG island is limited to the fetal DNA (as assessed by BssHII digestion). We further demonstrate that FMR-1 gene expression is repressed in the fetal tissue, as is characteristic of penetrant males, while the undermethylated chorionic villi expressed FMR-1. Since the genetic background of the tissues studied is identical, including the fragile X chromosome, these data indicate that the abnormal methylation of the FMR-1 CpG-island is responsible for the absence of FMR-1 transcription and suggests that the methylation may be acquired early in embryogenesis.

Base Sequence↗
PubMed1998

Attitude of potential users in Sicily towards preimplantation genetic diagnosis for beta-thalassaemia and aneuploidies.

This study aims to report the willingness of different populations of high-risk couples to undergo preimplantation genetic diagnosis (PGD) for beta-thalassaemia as an alternative to prenatal genetic diagnosis (PND), and the willingness of infertile couples to undergo PGD for aneuploidies. An information sheet and questionnaire presenting PGD and PND procedures were distributed to four population types: 54 high-risk couples for beta-thalassaemia coming for their first PND (population A); 51 similar couples coming for their second or further PND without previous experience of therapeutic abortion (population B-na); 50 similar couples coming for their second or further PND with previous experience of therapeutic abortion for beta-thalassaemia-affected fetus (population B-ab); and 74 infertile couples undergoing routine in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) (population C). Favourable first impressions towards PGD compared with PND were observed in all four populations in the following proportions: 79.6% population A; 76.5% population B-na; 92.0% population B-ab; and 96.0% population C. Willingness to undergo PGD for beta-thalassaemia was as follows: 44.4% population A; 47.1% population B-na; and 72.0% population B-ab. We conclude that previous experience of PND for beta-thalassaemia is a crucial point in the willingness to accept the PGD procedure, and that couples belonging to population B-ab are the most suitable to undergo PGD for beta-thalassaemia. Some 96.0% of infertile couples in population C were ready to undergo PGD for aneuploidies.

Abortion, Therapeutic↗
PubMed2000

Prenatal diagnosis of beta-thalassaemia using fetal erythroblasts enriched from maternal blood by a novel gradient.

We have assessed a new technique for the isolation of fetal erythroblasts from maternal blood for the non-invasive prenatal diagnosis of pregnancies at risk of beta-thalassaemia. This method relies on the separation of erythroblasts from maternal nucleated cells by a novel step gradient and high speed centrifugation. In four of the six cases examined, single erythroblasts were identified by immunohistochemistry for zeta (zeta) globin. These were individually micromanipulated and analysed by single cell polymerase chain reaction (PCR) and subsequent sequencing of the region of beta-globin locus where the mutations most common to the region of Puglia, Italy, are clustered. In each of the four instances where fetal erythroblasts were identified by antibody staining, the fetal beta-globin genotype was correctly determined. To date, this represents the largest series of non-invasive prenatal diagnoses performed for this haemoglobinopathy.

Centrifugation, Density Gradient↗
PubMed1999

Cure of beta-thalassaemia major by umbilical cord blood transplantation--a case report of Malaysia's first cord blood transplantation.

A 25-month-old boy with beta-thalassaemia major was presented with an opportunity for umbilical cord blood transplantation when his unborn sibling was diagnosed in utero to be a beta-thalassaemia carrier and also human leucocyte antigen compatible. A barely adequate amount of cord blood was collected at the birth of his sibling and infused into the patient after appropriate chemo-conditioning. Engraftment occurred without major complications. The subject is now alive and well 9 months post-transplant, thus marking our first success in umbilical cord blood transplantation.

Chorionic Villi Sampling↗
PubMed1989

Prenatal diagnosis of I-cell disease in the first and second trimesters.

First trimester prenatal diagnosis of I-cell disease (1 case) was based on demonstration of profound deficiency of N-acetylglucosamine 1-phosphotransferase in chorionic villi and in cultured trophoblasts derived from the chorionic villus specimen. Deficiency of this enzyme in cultured amniotic fluid cells obtained via amniocentesis was the basis for prenatal diagnosis of I-cell disease in the second trimester (2 cases). In both procedures, the diagnosis was corroborated by the finding of intracellular deficiency and extracellular elevation of multiple lysosomal enzymes in the fetal cell cultures (trophoblasts and amniotic fluid cells), as well as a significant increase in several lysosomal enzyme activities in the maternal serum.

Amniocentesis↗
PubMed2000

The challenge of prenatal diagnosis in twin pregnancies.

Prenatal diagnosis in multiple gestations poses unique problems. The use of screening modalities is limited, diagnostic procedures are more complicated, and the management of discordant results may be required. This article reviews work, both past and present, regarding these issues.

Amniocentesis↗