Report of 10 years of Karyotype results in fetuses following amniocentesis, referred to a Maternity hospital and the challenges of prenatal diagnosis for chromosome abnormalities

Introduction: Prenatal genetic diagnostic testing is intended to determine, with most certainty, whether a specific genetic abnormality is present in the fetus. Amniocentesis is the gold standard diagnostic techniques used for chromosome analysis in fetuses. Most of referrals for this test are abnormal maternal serum screening test.The aim of the study is to present the Cytogenetic data on amniotic fluid of more than 6000 fetuses referred to Sarem Women s .hospital in Tehran.Materials & Methods: A total of 6298 amniotic fluid samples for chromosome investigation were referred to the Cytogenetics laboratory of Sarem Maternity hospital. Karyotyping using standard procedures and GTG banding were carried out. When necessary, other bandings such as CBG, NOR, and other complementary techniques including FISH and Array-CGH techniques were conducted.Results: The success rate for obtaining a karyotype result was 99.7%. Most of the referrals were due to abnormal maternal serum screening test (71%). The overall chromosome abnormality rate was 5.1%. The highest chromosome abnormality belonged to Family history of chromosome abnormality (11.2%), followed by abnormal sonography (9.7%), raised maternal age (5.3%), and abnormal maternal screening (4.5%). Chromosomal polymorphism including pericentric inversion of chromosome 9, variations in the heterochromatin size of chromosomes 1, 9, 16, and Y as well as the satellite and NOR variations of acrocentric chromosomes were also present in some patients.Conclusion & discussion: While 5% of fetuses had abnormal karyotypes, 95% were normal. The polymorphisms were reported as normal population variant of no clinical significance. It is important to properly interpret the karyotype findings such as polymorphism, thus not creating stress and additional anxiety for the parents of the fetus. This highlights the fact that such diagnostic tests, mostly reassure couples for a normal fetus. The couples can make an informed decision about the continuation or termination of the pregnancy once they know about the abnormal karyotype of the fetus.

Keywords:

Prenatal Diagnosis , Karyotype , Abnormal maternal serum screening , chromosome polymorphism , inversion 9