The incidence of chromosomal anomalies in fetuses affected by mild renal pyelectasis.

Aim. The aim of this study was to evaluate the clinical significance of borderline fetal pyelectasis, whether it is associated with chromosomal aberration or is the expression of a structural defect of the urinary tracts.Methods. We carried out echographies on 2 900 pregnant women in the 2 n d trimester of their pregnancies between January 1998 and March 2002 at the Department of Obstetrics, Gynaecology and Neonatology. Any patient with fetuses affected by borderline pyelectasis in association with other echographic markers of aneuploidy and in women 35 years of age and older with fetuses presenting isolated pyelectasis underwent amniocentesis for karyotyping. Results. We discovered 2.1% (62 cases) of borderline pyelectasis in the general population. The karyotype was normal in all cases of isolated pyelectasis; 3/5 of the fetuses with borderline renal pyelectasts associated with other risk factors showed a chromosomal aberration. Conclusion. In accordance with existing documentation, the results of our research confirmed that isolated borderline pyelectasis does not increase the risk of chromosomopathies; this latter is significantly more frequent when pyelectasis is present in older pregnant women (>35 years of age) or is associated with other sonographic markers of chromosomal anomalies (choroids plexus cysts, cystic hygroma etc.). Prenatal cytogenetic tests of the fetal karyotype are to be recommended in older mothers and/or in presence of associated echographic anomalies. In this study we propose an early diagnosis of mild forms of pyelectasis which are misdiagnosed by superficial echographies, but which can be associated with chromosomopathy.