Spectrum of Chromosomal Abnormalities Detected by Conventional Cytogenetic Analysis Following Invasive Prenatal Testing of Fetuses with Abnormal Ultrasound Scans.

Objectives: The frequent association between malformations and chromosomal abnormalities is now well-established. This study looks at the incidence and type of chromosomal abnormalities detected by conventional cytogenetic analysis in women undergoing invasive tests following detection of fetal anomalies on antenatal scans as well as incidence of other genetic abnormalities detected by DNA analysis of fetuses with congenital anomalies that had a normal karyotype. Materials and Methods: A retrospective, observational study of pregnant women undergoing invasive testing following identification of fetal anomalies by ultrasonography was carried out in a tertiary care facility, Vellore, India, between 2011 and 2018. Results: 169 women underwent an invasive diagnostic procedure following detection of fetal anomalies. The most common indication for doing fetal karyotype was the presence of major fetal structural anomalies (142/169, 84%) with over a third (48/142, 34%) having multisystem involvement. Fetal hydrops was the next most common indication, detected in 18/169 (10%) fetuses. Aneuploidy was seen 19 of 25 fetuses (76%) with an abnormal karyotype with autosomal aneuploidy accounting for 13 (68%) and sex chromosome aneuploidy for seven (37%) of the fetuses. One fetus had double aneuploidy. In fetuses with normal karyotype, no additional information was obtained from further genetic testing. Conclusions: The overall detection rate of chromosomal abnormalities in our study using conventional cytogenetic analysis was 14.8%, the majority (72%) being associated with structural malformations, 20% with non-immune hydrops and 4% with soft markers. Abnormal karyotypes were seen in 12.7% of fetuses with structural malformations.