Sophisticated screening protocols for genetic abnormalities constitute an important component of current prenatal care, aiming to identify high-risk pregnancies and offer appropriate counseling to parents regarding their options. Definite prenatal diagnosis is only possible by invasive prenatal diagnostic testing (IPDT), mainly including amniocentesis and chorionic villous sampling (CVS). The aim of this comparative review was to summarize and compare the existing recommendations on IPDT from the most influential guidelines. All the reviewed guidelines highlight that IPDT is indicated based on a positive screening test rather than maternal age alone. Other indications arise from medical history and sonography, with significant variations identified between the guidelines. The earlier time for amniocentesis is unequivocally set at ≥15 gestational weeks, whereas for CVS, the earlier limit varies from ≥10 to ≥11 weeks. Certain technical aspects and the overall approach demonstrate significant differences. Periprocedural management regarding Rhesus alloimmunization, virologic status and use of anesthesia or antibiotics are either inconsistent or insufficiently addressed. The synthesis of an evidence-based algorithm for IPDT is of crucial importance to healthcare professionals implicated in prenatal care to avoid unnecessary interventions without compromising optimal prenatal care.

The Korean Society of Maternal Fetal Medicine proposed the first Korean guideline on prenatal aneuploidy screening and diagnostic testing, in April 2019. The clinical practice guideline (CPG) was developed for Korean women using an adaptation process based on good-quality practice guidelines, previously developed in other countries, on prenatal screening and invasive diagnostic testing for fetal chromosome abnormalities. We reviewed current guidelines and developed a Korean CPG on invasive diagnostic testing for fetal chromosome abnormalities according to the adaptation process. Recommendations for selected 11 key questions are: 1) Considering the increased risk of fetal loss in invasive prenatal diagnostic testing for fetal genetic disorders, it is not recommended for all pregnant women aged over 35 years. 2) Because early amniocentesis performed before 14 weeks of pregnancy increases the risk of fetal loss and malformation, chorionic villus sampling (CVS) is recommended for pregnant women who will undergo invasive prenatal diagnostic testing for fetal genetic disorders in the first trimester of pregnancy. However, CVS before 9 weeks of pregnancy also increases the risk of fetal loss and deformity. Thus, CVS is recommended after 9 weeks of pregnancy. 3) Amniocentesis is recommended to distinguish true fetal mosaicism from confined placental mosaicism. 4) Anti-immunoglobulin should be administered within 72 hours after the invasive diagnostic testing. 5) Since there is a high risk of vertical transmission, an invasive prenatal diagnostic testing is recommended according to the clinician\'s discretion with consideration of the condition of the pregnant woman. 6) The use of antibiotics is not recommended before or after an invasive diagnostic testing. 7) The chromosomal microarray test as an alternative to the conventional cytogenetic test is not recommended for all pregnant women who will undergo an invasive diagnostic testing. 8) Amniocentesis before 14 weeks of gestation is not recommended because it increases the risk of fetal loss and malformation. 9) CVS before 9 weeks of gestation is not recommended because it increases the risk of fetal loss and malformation. 10) Although the risk of fetal loss associated with invasive prenatal diagnostic testing (amniocentesis and CVS) may vary based on the proficiency of the operator, the risk of fetal loss due to invasive prenatal diagnostic testing is higher in twin pregnancies than in singleton pregnancies. 11) When a monochorionic twin is identified in early pregnancy and the growth and structure of both fetuses are consistent, an invasive prenatal diagnostic testing can be performed on one fetus alone. However, an invasive prenatal diagnostic testing is recommended for each fetus in cases of pregnancy conceived via in vitro fertilization, or in cases in which the growth of both fetuses differs, or in those in which at least one fetus has a structural abnormality. The guidelines were established and approved by the Korean Academy of Medical Sciences. This guideline is revised and presented every 5 years.

BACKGROUND: The Society of Obstetricians and Gynecologists of Canada and the Canadian College of Medical Genetics published guidelines, in 2011, recommending replacement of karyotype with quantitative fluorescent polymerase chain reaction when prenatal testing is performed because of an increased risk of a common aneuploidy.
OBJECTIVE: This study\'s objective is to perform a cost analysis following the implementation of quantitative fluorescent polymerase chain reaction as a stand-alone test.
RESULTS: A total of 658 samples were received between 1 April 2014 and 31 August 2015: 576 amniocentesis samples and 82 chorionic villi sampling. A chromosome abnormality was identified in 14% (93/658) of the prenatal samples tested. The implementation of the 2011 Society of Obstetricians and Gynecologists of Canada and the Canadian College of Medical Genetics guidelines in Edmonton and Northern Alberta resulted in a cost savings of $46 295.80. The replacement of karyotype with chromosomal microarray for some indications would be associated with additional costs.
CONCLUSIONS: The implementation of new test methods may provide cost savings or added costs. Cost analysis is important to consider during the implementation of new guidelines or technologies. © 2017 John Wiley & Sons, Ltd.

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The spread of both first trimester screening for chromosomal abnormalities and the possibility to check for single gene disorders at DNA-analysis has increased the request for chorionic villus sampling (CVS) in the first trimester. In order to perform placental biopsy, two routes are possible: the transcervical (TC) and the transabdominal (TA). In early days, the trancervical technique was the most diffused, but since its introduction into clinical practice, the TA technique has become the approach of choice in detriment of the TC technique. In our institution, we have a 30-year experience in TA-CVS with more than 26 000 procedures performed. Considering the expertise and the volume of procedures undertaken at our unit, we suggest a practical guideline for novel operators in TA-CVS.

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The prevalence of chromosomal abnormalities in clinically recognized early pregnancy loss is approximately 50% (1). Aneuploid fetuses account for 6-11% of all stillbirths and neonatal deaths (2). Chromosome defects compatible with life but causing significant morbidity occur in 0.65% of newborns, and another 0.2% have structural chromosomal rearrangements that will eventually affect reproduction (3). Although it is not possible to identify all aneuploidies antenatally, screening and diagnostic programs to detect the most common autosomal trisomy in liveborn infants, Down syndrome, are well established. This document will provide clinical management guidelines for the prenatal detection of these aneuploidies.

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These guidelines have been developed by the Association of Cytogenetic Technologists (ACT) for chromosome analysis. In formulating its recommendations, the task force reviewed guidelines established by several states and regional genetics groups. Draft guidelines prepared by the task force were reviewed by a panel of expert consultants, all of whom are laboratory directors and well known in their respective fields of expertise. The intention of the task force was to reflect procedures that are believed to be generally accepted by cytogenetic laboratories as basic criteria for effective chromosome analysis and that are consistent with existing cytogenetic quality assurance guidelines. It is important to stress that the primary purpose of the task force at this time is to establish guidelines for chromosome analysis. While the present guidelines address issues other than chromosome analysis, they do so incidentally and only in general terms. A more comprehensive discussion of other technical aspects of cytogenetics can be found in the forthcoming second edition of the ACT Cytogenetics Laboratory Manual. It is important to note that these guidelines are not intended to prescribe appropriate analyses for all individual circumstances. That determination is appropriately a matter for the judgment of the laboratories concerned. ACT, its members, and the task force that assisted in preparation of these guidelines make no warranty and assume no liability with respect to the information contained herein.