Search Results (2)

Diagnosis of a chromosome 22q11.2 microdeletion and its associated deletion syndrome (22q11.2DS) is optimally made early. We reviewed the available literature to provide contemporary guidance and recommendations related to the prenatal period. Indications for prenatal diagnostic testing include a parent or child with the 22q11.2 microdeletion or suggestive prenatal screening results. Definitive diagnosis by genetic testing of chorionic villi or amniocytes using a chromosomal microarray will detect clinically relevant microdeletions. Screening options include noninvasive prenatal screening (NIPS) and imaging. The potential benefits and limitations of each screening method should be clearly conveyed. NIPS, a genetic option available from 10 weeks gestational age, has a 70–83% detection rate and a 40–50% PPV for most associated 22q11.2 microdeletions. Prenatal imaging, usually by ultrasound, can detect several physical features associated with 22q11.2DS. Findings vary, related to detection methods, gestational age, and relative specificity. Conotruncal cardiac anomalies are more strongly associated than skeletal, urinary tract, or other congenital anomalies such as thymic hypoplasia or cavum septi pellucidi dilatation. Among others, intrauterine growth restriction and polyhydramnios are additional associated, prenatally detectable signs. Preconception genetic counselling should be offered to males and females with 22q11.2DS, as there is a 50% risk of transmission in each pregnancy. A previous history of a de novo 22q11.2 microdeletion conveys a low risk of recurrence. Prenatal genetic counselling includes an offer of screening or diagnostic testing and discussion of results. The goal is to facilitate optimal perinatal care. Full article

Chromosomal mosaicism is one of the primary interpretative issues in prenatal diagnosis. In this review, the mechanisms underlying feto-placental chromosomal mosaicism are presented. Based on the substantial retrospective diagnostic experience with chorionic villi samples (CVS) of a prenatal diagnosis laboratory the following items are discussed: (i) The frequency of the different types of mosaicism (confined placental, CPM, and true fetal mosaicisms, TFM); (ii) The risk of fetal confirmation after the detection of a mosaic in CVS stratified by chromosome abnormality and placental tissue involvement; (iii) The frequency of uniparental disomy for imprinted chromosomes associated with CPM; (iv) The incidence of false-positive and false-negative results in CVS samples analyzed by only (semi-)direct preparation or long term culture; and (v) The implications of the presence of a feto-placental mosaicism for microarray analysis of CVS and non-invasive prenatal screening (NIPS). Full article