FETAL MILD IDIOPATHIC LATERAL VENTRICULOMEGALY - IS THERE A CORRELATION WITH FETAL TRISOMY

Mild idiopathic lateral ventriculomegaly in the mid-trimester fetus ca n be accurately detected using modern prenatal ultrasonography. Since an abnormal karyotype has been reported in some of these cases, the pr esent prospective study was designed to evaluate, first, the prevalenc e of mild idiopathic lateral ventriculomegaly in the general obstetric population and, second, to determine the incidence of abnormal fetal karyotype associated with mild idiopathic lateral ventriculomegaly. Ei ght cases of mild idiopathic lateral ventriculomegaly (0. 15%) were de tected among 5400 routine prenatal sonographic examinations, between 1 6 and 22 weeks' gestation. Three new-born infants were found to be nor mal; in one baby, spontaneous resolution of the lesion occurred in ute ro, and, among the other five cases, two had an abnormal karyotype: on e had Down's syndrome, and one trisomy 18. A review of the English lit erature revealed that 12% of fetuses with mild idiopathic lateral vent riculomegaly have an abnormal karyotype. Since 3% of the fetuses with Down's syndrome can be visualized in utero with mild idiopathic latera l ventriculomegaly, the calculated risk for Down's syndrome when such lesions appear is about 3%. We, therefore, conclude that karyotypic st udy is warranted in the mid-trimester fetus with incidental findings o f mild idiopathic lateral ventriculomegaly.