Sonographic features of trisomy 18 at midpregnancy

OBJECTIVE: To evaluate the sonographic characteristics of the fetuses with trisomy 18 at 16-22 weeks of gestation. METHODS: The subjects were recruited from pregnant women undergoing prenatal sonographic examinations at 16-22 weeks of gestation and subsequently proven to be trisomy 18. The results of ultrasound findings were retrospectively reviewed in 25 cases with chromosomes which were confirmed as trisomy 18. RESULTS: All cases had at least one abnormal sonographic finding. There was only one case that had no structural abnormality, but fetal growth restriction was documented. The common sonographic findings included fetal growth restriction, choroid plexus cysts, cardiac anomalies, clenched hand, omphalocele and cleft lip. Fetal growth restriction was the most common finding demonstrated in nearly half of all cases. Other less common findings were diaphragmatic hernia, abnormal head shape, polyhydramnios, single umbilical artery. CONCLUSION: Nearly all fetuses with trisomy 18 had characteristic sonographic patterns of abnormalities demonstrated at midpregnancy. Detailed ultrasound at midpregnancy could effectively screen fetuses with trisomy 18 for further genetic testing.