Analysis of Antenatal Sonographic Features of the Fetuses with Trisomy 21

To evaluate the second trimester ultrasound findings of the fetuses with Down syndrome.
Patients and We conducted a retrospective analysis of 781 patients who underwent prenatal invasive test between November 2011 and July 2015. Based on the patients’ medical records, the demographic data and second trimester ultrasound findings of the fetuses with Down syndrome were retrospectively analyzed.
Trisomy 21 was detected in 26 (3.3%) patients. The median (min-max) maternal age of trisomy 21 cases was 31.9 (17 - 41) years. The karyotype indications were high risk in the combined test, triple test, quadruple test and pathologic findings on the ultrasound examination. One case in the ultrasound group had both of combined test and triple test in the low risk area. In this patient, ultrasound examination revealed talipes equinovarus and delayed chorioamniotic fusion at 27 weeks of gestation. Trisomy 21 was detected in four patients by chorion villus biopsy at the first trimester. Second trimester ultrasound was performed in 22 out of these 26 women. However, there were sonographic findings in only 16 (72.7%) patients. Six (27.2%) fetuses had no minor or major anomaly at the detailed ultrasound examination. The frequency of major cardiac anomaly was 22.7%. Choroid plexus cyst and aberrant right subclavian artery were the single findings in two fetuses at the second trimester ultrasound exam.
Although the sensitivity of second trimester genetic ultrasound for detection of fetal Down syndrome at our perinatology unit was rather high, nearly one of three patients with Down syndrome had no detectable sonographic finding. Second trimester ultrasound alone is not strong enough to exclude the diagnosis of Down’s syndrome