Objective: Our aim was to evaluate the risk of chromosomal abnormalities esp. trisomy 18, associated with isolated choroid plexus cyst(s) in pregnant women undergoing second-trimester ultrasonographic examination. Design: A review article. Setting: OBGYN clinic of the 1st faculty of medicine, Prague, Teaching hospital Bulovka. Subject: Choroid plexus cyst(s) (CPC) are more common in fetuses with chromosomal aneuploidies, particularly trisomy 18. Although it is accepted that the risk of karyotypic abnormality justifies amniocentesis in the case of other associated abnormalities are present, disagreement continues as to the risk of trisomy 18 in a fetus with an isolated choroid plexus cyst. We evaluated additional consideration of maternal age and multiple-marker screening for chromosomal aneuploidy in the assessment of risk. Case report: We report a trisomy 18 case that was diagnosed on the basis of CPC detection by ultrasound, NMR, and further amniocentesis. Conclusion: It is well accepted that choroid plexus cyst(s) in association with other congenital anomalies warrant amniocentesis to determine fetal karyotype. The presence of isolated CPC varies around 1% in general population, but around 30% in fetuses with trisomy 18 where the prevalence is 3 per 10,000 pregnancies. Metaanalyses reported incidence of trisomy 18 of 1 in 374 in fetuses with isolated CPC. These risks do not exceed the 1:200 risk of pregnancy loss after amniocentesis and also the 1:270 risk of Down syndrome (DS) in a 35-year-old woman, but exceeds the risk for DS of a 37-year-old woman. Thus these findings suggest that amniocentesis should not be offered to pregnant women in the presence of isolated fetal choroid plexus cyst(s), but in the absence of other pathologies. Amniocentesis is then justified only in the patient with advanced maternal age.

        Key words: choroid plexus cyst, trisomy 18, maternal age, multiple-marker screening