Objective:Presentation of agenesis/hypoplasia of kidneys and cystic kidneys in the Czech Republic during 1961 –2000.Analysis of prevalence of these defects in different groups by maternal age.Design:Retrospective demographic-epidemiological study. Setting:Institute for the Care of Mother and Child,Prague. Method:The author used data from the nationwide register o birth defects in neonates,kept by the Institute of Health Information and Statistics in the CR during 1990 –2000.Epidemiological analysis of the incidence of agenesis/hypoplasia of the kidneys and cystic kidneys in the CR during 1961 to 2000 in cases diagnosed prenatally and in born children.The authors made a mathematical-statistical analysis of the prevalence of these defects by maternal age,using the method of calculation of the 95%confidence interval of probability. Results:In the CR there were during the period from 1961 –2000 1093 registred cases of agenesis/hypoplasia o the kidneys and 1370 cases of cystic kidneys.The mean incidence during the entire period was 1.81 in agenesis/hypoplasia of the kidneys and 2.26 in cystic kidneys per 10 000 live born infants.After adding prenatally diagnosed cases and pregnancies terminated on that account it was 2.05 a 2.58 per 10 000 live born infants. Conclusion:The investigation of these inborn defects did not confirm nor rule out statistically a higher risk of women older than the population average.

        Key words: inborn defect,agenesis/hypoplasia of kidneys,cystic kidneys,incidence,Czech Republic,prenatal diagnosis,maternal age