Three- and 4-dimensional ultrasonography in the prenatal evaluation of fetal anomalies associated with trisomy 18.

OBJECTIVE: The purpose of this study was to assess the usefulness of 3- and 4-dimensional ultrasonography (3D/4DUS) for the description of anomalies associated with trisomy 18 and to determine whether 3D/4DUS adds diagnostic information over what is provided by conventional 2-dimensional ultrasonography (2DUS) alone.

METHODS: Twenty-six fetuses subsequently proven to have trisomy 18 underwent prenatal ultrasonographic evaluations by both 2DUS and 3D/4DUS. Volume data sets were acquired by the same sonographers after the conventional 2DUS examinations and were explored with 4-dimensional imaging software by another independent examiner blinded to the indications of 2DUS. The findings detected by 2DUS and 3D/4DUS were compared with those acquired at autopsy. The sensitivity of each modality for detecting anomalies was calculated and compared by the McNemar test.

RESULTS: Excluding polyhydramnios, there were 131 anomalies confirmed postnatally in 26 fetuses with trisomy 18. There was a statistically significant difference in the sensitivity for detecting anomalies between 3D/4DUS and 2DUS (93.89% versus 73.28%; McNemar value = 23.31; P < .05), especially in anomalies of the face/neck (96.15% versus 65.38%; McNemar value = 6.13; P < .05) and extremities (96.3% versus 48.15%; McNemar value = 11.07; P < .05). Three- and 4-dimensional ultrasonography provided additional diagnostic information for 83.97% of the anomalies related to trisomy 18 and influenced the obstetric management of 4 fetuses.

CONCLUSIONS: Three- and 4-dimensional ultrasonography offered diagnostic advantages for many anomalies associated with trisomy 18, especially for anomalies of the extremities and face. This modality could be a powerful adjunct to 2DUS in the prenatal anatomic evaluation of fetuses with trisomy 18.