We report the ultrasound detection of cranial abnormalities in a fetus with partial trisomy 9 (pter-q22) and partial trisomy 21 (q22.3-qter) due to a 3:1 segregation with tertiary aneuploidy transmitted from a maternal reciprocal translocation 9;21. Prenatal sonographic findings of the proband at 24 gestational weeks manifested bilateral dilated lateral ventricles, an enlarged cisterna magna and intrauterine growth retardation. Though rare, both trisomy 9 and partial trisomy 9 are distinct entities in infants (Schinzel, 1993(Schinzel, , 1994)). Prenatal diagnosis and sonographic findings of mosaic or non-mosaic trisomy 9 are also well-documented. However, in utero sonographic appearances of fetal partial trisomy 9 in early pregnancy, to our knowledge, have not been previously described. Our report adds to the understanding of the prenatal manifestations of fetuses with partial trisomy 9, as well as the significance of genetic counselling.
This was the third pregnancy of a 41-year-old, gravida 5, para 2, healthy Chinese woman who had two normal children. In this pregnancy, she was advised to receive carrier testing for possible familial chromosomal translocation. This was because her sister, a 34-year-old, gravida 4, para 1, woman, had just undergone genetic amniocentesis for advanced maternal age. The result showed an unexpected balanced reciprocal translocation of 46,XX,t(9;21)(q22;q22.3) (Fig. 1) in both fetus and her sister. In the present case, cytogenetic analysis of the mother showed a balanced