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Choroid plexus cysts (CPC) in the fetus are still the subject of considerable debate in the literature. Because of their association with aneuploidy, and especially with trisomy 18, of which they are an ultrasonographic marker, the detection of fetal CPC now poses the problem of how these cases should be managed, since most occur in young women (there being no correlation between CPC and age), and since the incidence among the general population is fairly high (around 1%). With the aim of contributing further to the debate, a retrospective study was performed of all cases of fetal CPC diagnosed in our Centre between January 1984 and August 1994, together with a review of the relevant literature. There were 95 cases of fetal CPC with complete neonatal and necroptic data available. These cases included women recruited in the course of routine screening for congenital malformations carried out in our Centre at 14 and 21 weeks gestation, women referred to us from other Centres, and women recruited in the course of amniocentesis indicated for those aged over 35. In all cases in which fetal CPC was detected, a careful ultrasonographic examination was performed to exclude the presence of even the smallest morphologic anomaly. Whenever the fetus was found to have an anomaly karyotyping was done. If the CPC was not associated with any morphologic anomaly, karyotyping was proposed only to those women at risk of aneuploidy because of their age. There were 11 cases of trisomy 18, all of which presented morphologic anomalies associated with CPC. Some of these anomalies where "minor", however, and therefore difficult to assess even when a careful ultrasonographic examination was performed by an experienced operator (Intra ventricular septal defect, single umbilical artery). In 2 cases, CPC was associated with trisomy 21. Both women were aged over 35. All the other cases of CPC not associated with morphologic anomaly were normal on postnatal examination. From a meta-analysis of the literature, two distinct management protocols emerge for the problem of "isolated CPC detected at ultrasonographic examination". One group of authors recommends karyotyping for all women with fetal CPC, considering the presence of CPC in itself a risk factor for aneuploidy. The second group, to which we ourselves belong, believes it is sufficient to perform a careful ultrasonographic examination so as to exclude the presence of other morphologic anomalies associated with the CPC. Karyotyping should be proposed only to women at risk of aneuploidy because of their age (> 35). A review of the biggest series reported in the literature shows that, of a total of 1670 fetuses with CPC, 94 were trisomy 18. None of the cases of CPC "in isolation" emerged as being associated with this aneuploidy. However, numerous cases of trisomy 18 have been described in which CPC is associated with "minor" morphologic anomalies in the fetus which may be difficult to detect. It is therefore essential to perform a careful ultrasonographic examination in all cases of CPC, preferably in a Centre with specialist knowledge of ultrasonography. If this option is not available, then karyotyping of all women with fetal CPC is clearly advisable.

The clinical significance of the fetal choroid plexus cysts, observed by prenatal sonographic examination, is now a days still discussed. A consequence of this situation is the discordance of opinions about the question of whether karyotype analysis is always necessary to evaluate chromosomal anomalies sometimes correlated, especially in the presence of (as some authors have reported) large (> 1 cm), bilateral, persistent cysts and of other structural abnormalities. We have effected a prospective study to estimate the incidence of fetal choroid plexus cysts and to establish the obstetrical behaviour to be adapted in these cases. During 834 routine ultrasonographic examinations at 18-21 weeks' gestational age, we have evaluated the presence of fetal choroid plexus cysts in 9 fetuses, with an incidence of 1.07%. Three of these cysts were larger than 1 cm, three were bilateral. Karyotype analysis, effected in all cases, diagnosed a case of Trisomy 18 in a fetus who ultrasonographically showed, in addition to a unilateral cyst of 1.2 cm, also a diaphragmatic hernia. Careful ultrasound follow-up revealed that all the cysts disappeared spontaneously, but two of them (whose dimensions were larger than 1 cm) were still visible at 24 weeks' gestation and probably this age will be too advanced to begin a chromosome analysis. In conclusion, we think that the presence of fetal choroid plexus cysts always imposes a careful ultrasonographic evaluation of fetal morphology and, since there is always the risk that other small fetal anomalies (evocative of abnormal fetal karyotypes) wight not be noted, we believe that it is better, in any case, to recommend to the patient a prenatal cytogenetical analysis.

Twenty-six cases of fetal choroid plexus cysts were diagnosed using ultrasonography at the Ultrasound Out-patients clinic of the University of Turin during the period 1989-1991. In 21 of these cases fetal karyotype was ascertained since, as has been reported in the literature, cysts of the choroid plexus may be associated with an anomalous karyotype (trisome 18 or 21). One of the 21 cases had an altered karyotype (trisome 21) (4.2%). The Authors stress the importance of a detailed ultrasound study of fetal morphology since, in the presence of structural anomalies, the incidence of trisome 18 is much higher. On the basis of these data, prenatal diagnosis in the event of the echographic presence of choroid plexus cysts appears to be valid since the risk of chromosome anomalies is much higher than in 35-year-old women.