[Prenatal screening for cysts of choroid plexus. Evolution and interpretation of 30 cases]

The authors report thirty cases in which they diagnosed a cyst of the choroid plexus antenatally between the 18th and the 36th week of amenorrhoea (mean 21 weeks). Choroid plexus cysts show up in some pictures as round or oval cysts clearly visible in the region of the choroid plexus. They appear in the lateral cerebral ventricles. They frequently occur between the 15th and 25th week of amenorrhoea (0.6 to 2.5% of pregnancies), unilaterally or bilaterally (46%) either on the right of left side and varying in size (3 to 20 mm). These characteristics do not influence the way they evolve. If a single choroid plexus cyst is found a control ultrasound should be carried out four weeks later. 96% of them have disappeared by the end of the second trimester; but if they do persist in the third trimester (4%) they are not necessarily pathological. On the other hand if a choroid plexus cyst is associated with some other morphological biometric abnormality antenatal chromosome testing should be carried out because trisomy 18 is more common in this situation (4.8%) than in the general population.