[Fetal malformations diagnosed using ultrasonography during tri-test. A retrospective study of 1633 fetuses]

To find out which fetal malformations are diagnosed during the tri-test.

A total of 1633 pregnant women were enrolled in the study and underwent biochemical screening for Down s syndrome and DTN at the Outpatient Clinic for Prenatal Diagnosis of Santo Bambino Hospital in Catania between January 1997 and December 1998. Scans were performed using a TA route in all cases and mainly during the 16th week.

21 abnormal fetuses were diagnosed, equal to 1 out of 77 fetuses (3 cases of isolated DTN; 1 case of cyst in the posterior cranial fossa associated with complex heart malformation; 6 cases of cyst of the choroid plexus; 2 cases of bone dysplasia; 2 cases of cardiopathy; 4 cases of non-immunological fetal hydrops; 1 case of hygroma). In 8 out of 21 abnormal fetuses the tri-test was positive for DNT and SD or atypical. One case of trisomy 18 and 1 case of mosaicism were diagnosed.

A fetal abnormality was diagnosed in one out of 77 fetuses. This finding, although it underestimates the real frequency of these anomalies (retrospective study, selected sample, non optimal period for the diagnosis of fetal malformations, non-systematic study of 4 chambers), once again underlines the importance of a careful morphological evaluation in eyery scan carried out. In our study some malformations were not diagnosed previously because this was the first scan (1 case of anencephaly), or because the abnormality was presumably not present in earlier tests (bone dysplasia at early stage of pregnancy) or because the earlier test was inadequate (2 DTN tested after the 12th week). In some cases it is also possible to diagnose images, such as transient hygromas which indicate a group of patients with a risk of chromosome pathology. Since they are transient, these lesions are only found if the test is performed at a period of pregnancy before the optimal moment for the tri-test. In personal experience the execution of biochemical screening for Down s syndrome and DTN should always be associated with a scan not only to date the pregnancy, but also because it is not infrequent to diagnose malformations.