Ultrasound imaging of fetal neck anomalies: implications for the risk of aneuploidy and structural anomalies.

This study summarizes 24,000 transvaginal ultrasound examinations which were performed in a predominantly low-risk population at 14-16 weeks' gestation. 1254 (5.2 per cent) fetuses had a nuchal fold or a non-septated cystic hygroma. Of these fetuses, 140 (11.1 per cent) had additional structural anomalies. Cardiovascular anomalies were the most commonly detected structural malformations. Forty-three (3.4 per cent) fetuses were aneuploid. Trisomy 21 was the most common chromosomal anomaly (n = 27). Aneuploidy was significantly more common in fetuses who had a nuchal finding and an associated structural anomaly. The prevalence of nuchal fold and non-septated cystic hygroma, as well as the incidence of their associated structural anomalies, was similar. Based on these data, it is concluded that a complete ultrasonic survey of the fetus and karyotyping are advocated in fetuses with a nuchal abnormality, irrespective of maternal age or triple serum screening results.