The nuchal translucency examination leading to early diagnosis of structural fetal anomalies

To evaluate the ability to diagnose structural fetal anomalies during or soon after an extended nuchal translucency (NT) examination.

The study population included all women who had a routine NT examination in the ultrasound division of one of three centers. Also included in the study were women referred to these centers following an abnormal NT examination. The sonographers were instructed to pay attention to fetal anomalies while performing the NT examination. Each examination was initially attempted transabdominally. Failure to obtain adequate views transabdominally was an indication for a transvaginal examination. When a structural fetal anomaly was detected or suspected, a full fetal anomaly scan was performed. When a diagnosis could not be established, fetal anatomy scan was repeated after 14 weeks of gestation. Fetal cardiac scanning was performed transvaginally, immediately or within 3 days after an increased NT was observed. When fetal anomalies were diagnosed the patients were informed about the possibilities of terminating the pregnancy or continuing the work-up and follow-up. Overall, ascertainment of fetal outcome was available in 85% of the study population.

We performed 4467 NT examinations during the study period and additional 123 fetal cardiac scanning following an abnormal NT examination. Overall, we performed 365 fetal cardiac scanning between 11 and 14 weeks of gestation. The fetal anomalies detected included the following: three skeletal anomalies, seven brain anomalies, four urinary system anomalies, four abdominal anomalies, two facial anomalies, and 13 cardiac anomalies. Six of the 13 cardiac anomalies were found in the atrioventricular canal. One third of the patients (11/33) elected to discontinue the pregnancy a short time after the detection of the congenital anomaly (until 14 weeks of gestation) and half of the patients (16\33) asked for termination of pregnancy later. More than 60% of the patients (20/33) with congenital anomalies detected following the NT examination refused to have chorionic villous sampling (CVS) or amniocentesis.

The opportunity to scan the fetal anatomy in the early stages of pregnancy, when the NT examination is performed, justifies the approach of extended NT examination.