Prenatal diagnosis of Down syndrome in dizygotic twin pregnancy (original) (raw)
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Twin Pregnancy discordordant for Downs syndrome: Case Report
International Journal of Medical Research and Review
The work presented is a clinical and genetical trial of a couple with a reproductive failure and a family history of chromosomal abnormalities. The most reliable and accurate methods used for antenatal diagnosis of Down syndrome fetuses are highlighted.
Human Reproduction, 2008
† Introduction † Materials and Methods † Results † Discussion † Funding † Acknowledgements † References background: Previous studies have found that 1 in 10 in vitro fertilization (IVF) singletons originates from a twin gestation. First trimester Down's syndrome screening markers are altered in assisted reproductive techniques (ART) pregnancies compared with spontaneously conceived pregnancies. The presence of a perished embryo may further complicate prenatal screening among women pregnant after ART. The aim of this study was to assess the impact of a 'vanishing twin' on first trimester combined biochemical and ultrasound screening in pregnancies conceived after IVF and intracytoplasmatic sperm injection. methods: From a national prospective cohort study concerning first trimester combined screening among women pregnant after ART, 56 cases of pregnancies with a vanishing twin were identified. As control group 897 cases of ART singleton pregnancies were used. All women completed a first trimester combined ultrasound and biochemical screening programme comprising serum PAPP-A and free b-hCG together with nuchal translucency (NT) measurement. results: There were no significant differences in geometric mean MoM free b-hCG and PAPP-A between pregnancies with an early (gestational week ,9, EVT) or late vanishing twin (gestational week 9-13, LVT) or singleton pregnancies (0.98, 1.13 and 0.95 for free b-hCG and 0.84, 0.80 and 0.74 for PAPP-A, respectively). Likewise, no difference was seen for NT measurements. The gestational age at the time of blood sampling and NT scan was similar for the three groups. The proportion of EVT pregnancies with a PAPP-A and free b-hCG log 10 MoM value below the 5th%iles and above the 95th%iles of the value in the singleton pregnancies were 4.3%, 4.3%, 6.4% and 8.5%, respectively, which did not constitute a significant difference from singletons. The corresponding values for LVT pregnancies were 0%, 22.2%, 0% and 11.1%, respectively; however, these numbers were too small to allow for statistical calculations. conclusions: First trimester biochemical screening markers in women pregnant after ART, and with a vanished twin diagnosed at early ultrasound, do not differ from those of other ART singleton pregnancies. In cases where the fetal demise was first diagnosed at the time of the NT scan, it is doubtful whether the serum risk assessment is as precise as it is in singleton ART pregnancies. No difference was seen for NT measurements.
American Journal of Obstetrics and Gynecology, 1996
OBJECTIVE: Our purpose was to study prospectively the use of ultrasonographic biometry to refine the risk estimates for both Down syndrome and any clinically significant chromosome defect in women with abnormal biochemical triple-screen results. STUDY DESIGN: Ultrasonographic biometry and anatomic survey were performed on study and control cases. Expected values for humerus, femur, combined humerus plus femur lengths, and abdominal circumference were generated on the basis of biparietal diameter obtained from a normal group. Threshold observed/expected values of each measurement for screening for Down syndrome and clinically significant chromosome defects were determined with receiver-operator characteristic curves. By stepwise logistic regression analysis the optimal screening parameters, including nuchal thickness, for detection of Down syndrome and clinically significant chromosome defect were determined. Risk tables for chromosome anomalies were developed on the basis of ultrasonography and triple-screen values. RESULTS: Of 1034 cases at risk for Down syndrome (risk >1/270) or trisomy 18 on the basis of triple-screen results, there were 11 cases of Down syndrome, 1 of trisomy 18, and 17 clinically significant chromosome defects. Abnormal nuchal thickness or observed/expected humerus length <0.92 was the most sensitive parameter for Down syndrome detection. Abnormal nuchal thickness or observed/expected combined femur and humerus length <0.90 was the most sensitive for significant chromosome defects. With abnormal biometry or anatomy the Down syndrome risk was 8 of 127 versus 1 of 753 in normals, odds ratio 50.4 (95% confidence interval 6.4 to 90.2), p < 0.00001, and the risk of significant defects was 11 of 90 versus 6 of 830 in normals, odds ratio 19.3 (95% confidence interval 6.4 to 60.5), p < 0.00001. In a pregnancy with a 1 in 270 triple-screen risk for Down syndrome, normal biometric and anatomic results reduce the risk to 1 in 2100. CONCLUSION: Normal ultrasonographic anatomy and biometry significantly reduces the risk of both Down syndrome and any significant chromosome defects in pregnancies with abnormal triple-screen results. (Am J Obstet Gynecol 1996;175:824-9.) Key words: Down syndrome, ultrasonography Between 25% and 30% of women at increased Down syndrome risk on the basis of midtrimester triple-analyte biochemical screening decline genetic amniocentesis. This percentage is even higher among women >36 years old. ~ There is no correlation between the actual level of Down syndrome risk on the basis of biochemical screening and the decision to undergo genetic amniocentesis until that risk becomes >1 in 50. 2, 3 Because of the low positive predictive value of an abnormal triple-screen result for Down syndrome, there is a need to improve the
Prenatally detected double trisomy: Klinefelter and Down syndrome
Prenatal Diagnosis
Double trisomies are a rare occurrence. We report the first case of a Down and Klinefelter's syndrome (48,XXY,+21) in a fetus that was prenatally diagnosed during the 15th week of pregnancy. Even though the nasal bone was present, and the color-Doppler study of the ductus venosus and the nuchal thickness were normal, the maternal serum test results indicated an increased risk of Down syndrome and consequentially a genetic amniocentesis was performed. A 48,XXY,+21 karyotype was observed and the patient decided to terminate the pregnancy. In this case, we did not find the typical ultrasound (US) signs that would have led us to the chromosomopathy; furthermore, we emphasize the advantages of using biochemical screening which, in our case, were crucial in arriving at the correct diagnosis.
PRENATAL SCREENING FOR FETAL ANEUPLOIDY, DOWN’S SYNDROME, WHO, WHOM, WHY & HOW?????
Chromosomal abnormalities occur in 0.1% to 0.2% of live births; Trisomy 21 (Down syndrome) is the most common karyotype abnormality in live-born infants (1 per 800 live births. Trisomy 21 is the most common genetic cause of mental retardation and one of the few aneuploidies compatible with post-natal survival. The vast majority of meiotic errors leading to the trisomic condition occur in the egg, as nearly 90% of cases involve an additional maternal chromosome. The severity of each of the phenotypic features is highly variable among the patients. Besides mental retardation, present in every individual with Down syndrome (DS), Trisomy 21 is associated with more than 80 clinical traits including congenital heart disease, duodenal stenosis or atresia, imperforate anus, Hirschprung disease, muscle hypotonia, immune system deficiencies, increased risk of childhood leukemia and early onset Alzheimer's disease. The rapid changes in prenatal screening and diagnostic techniques bring new challenges Developments in Trisomy 21 (Down syndrome) screening have sought to increase sensitivity and specificity of screening tests.Various methods have been used to identify women at risk of carrying a fetus with Trisomy 21, including consideration of maternal age, biochemical markers, amniocentesis and prenatal ultrasound. This article reviews the literature on prenatal screening for Down’s syndrome which is evidence based and this extensive literature examines how appropriate widely-held understandings of Down’s syndrome are, and asks whether or not practitioners and prospective parents have access to the full range screening and diagnostic test and keeping in account moral, ethical, social &financial milieu of the region and from the point of view of a regional foetal medicine unit. From the point of view of the individual woman, this means that if she chooses to participate in screening, she will have a high chance of detection of Down syndrome, and a low chance that a subsequent invasive diagnostic test will be recommended when her baby is unaffected, since invasive testing carries a low but measurable risk of foetal death.
The genetic sonogram: a method of risk assessment for Down syndrome in the second trimester
Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine, 2002
To determine the risk of Down syndrome in fetuses with sonographic markers using the Bayes theorem and likelihood ratios. We prospectively evaluated the midtrimester sonographic features of fetuses with Down syndrome and compared them with euploid fetuses. Patients were referred for an increased risk of aneuploidy and evaluated for the presence of structural defects, a nuchal fold, short long bones, pyelectasis, an echogenic intracardiac focus, and hyperechoic bowel. All fetuses underwent amniocentesis at the time of sonographic assessment. The sensitivity, specificity, and likelihood ratios for markers were calculated both as nonisolated and isolated findings. There were 164 fetuses with Down syndrome and 656 euploid fetuses. The presence of any marker resulted in sensitivity for the detection of Down syndrome of 80.5% with a false-positive rate of 12.4%. The absence of any markers conferred a likelihood ratio of 0.2, decreasing the risk of Down syndrome by 80%. As an isolated mark...
Trisomy 21 in both fetuses in a DCDA twin pregnancy
BMJ Case Reports, 2019
A woman’s chances of having a child with Down syndrome increases with age. By age 40, the risk of conceiving a child with Down syndrome is about 1 in 100. We report a rare case of dizygotic dichorionic diamniotic twin pregnancy conceived via in vitro fertilisation, with both twins having trisomy 21. Both fetuses were independently detected to be at high risk of autosomal trisomy, initially via first-trimester screening and subsequently via invasive definitive diagnostic tests (ie, chorionic villus sampling and amniocentesis).Diagnosis of trisomy 21 has to be made via initial non-invasive prenatal screening, followed by further rigorous and accurate invasive pregnancy testing for confirmation. The gravity of the results necessitates high detection rates and high specificity of prenatal screening tests. Management of the patient must be multidisciplinary and supportive in nature, involving extensive and non-directive pregnancy counselling and management, genetic counselling and manage...
Prenatal Screening for and Diagnosis of Aneuploidy in Twin Pregnancies
Journal of Obstetrics and Gynaecology Canada, 2011
Objective: To provide a Canadian consensus document with recommendations on prenatal screening for and diagnosis of fetal aneuploidy (e .g ., Down syndrome and trisomy 18) in twin pregnancies. Options: The process of prenatal screening and diagnosis in twin pregnancies is complex. This document reviews the options available to pregnant women and the challenges specific to screening and diagnosis in a twin pregnancy. Outcomes: Clinicians will be better informed about the accuracy of different screening options in twin pregnancies and about techniques of invasive prenatal diagnosis in twins. Evidence: PubMed and Cochrane Database were searched for relevant English and French language articles published between 1985 and 2010, using appropriate controlled vocabulary and key words (aneuploidy, Down syndrome, trisomy, prenatal screening, genetic health risk, genetic health surveillance, prenatal diagnosis, twin gestation). Results were restricted to systematic reviews, randomized controlled trials, and relevant observational studies. Searches were updated on a regular basis and incorporated in the guideline to August 2010. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. The No. 262 (Replaces No. 187, February 2007) This document reflects emerging clinical and scientific advances on the date issued and is subject to change. The information should not be construed as dictating an exclusive course of treatment or procedure to be followed. Local institutions can dictate amendments to these opinions. They should be well documented if modified at the local level. None of these contents may be reproduced in any form without prior written permission of the SOGC. This clinical practice guideline has been prepared by the Genetics Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) and the Prenatal Diagnosis Committee of the Canadian College of Medical Geneticists (CCMG) and approved by the Executive and Council of the Society of Obstetricians and Gynaecologists of Canada and the Board of Directors of the Canadian College of Medical Geneticists.