OBJECTIVE: To measure the intracranial translucency (IT) and the cisterna magna (CM), to produce reference ranges and to examine the interobserver and intraobserver variability of those measurements. To examine the possible association of IT with chromosomal abnormalities. METHODS: Prospective study on pregnancies assessed at 11 to 14 weeks. IT was measured retrospectively in 17 cases with aneuploidy. RESULTS: To produce reference ranges, 465 fetuses were used. IT and CM correlated linearly with crown-rump-length (CRL) and were independent of maternal demographic characteristics and biochemical indices. IT had a weak positive correlation with nuchal translucency. For IT the intraclass correlation coefficient was 0.88 for intraobserver variability and 0.83 for interobserver variability. For CM the intraclass correlation coefficient was 0.95 for intraobserver variability and 0.84 for interobserver variability. The IT multiple of the median was significantly increased in the chromosomally abnormal fetuses (1.02 for the normal and 1.28 for the chromosomally abnormal fetuses, Mann Whitney p < 0.001). IT multiple of the median was a significant predictor of chromosomal abnormality (Receiver Operator Characteristic curve analysis: Area under the curve = 0.86, CI=0.76-0.96, p<0.001). CONCLUSION: Intracranial translucency and CM can be measured reliably at the 11 to 14 weeks examination and the measurements are highly reproducible. IT appears to be increased in fetuses with chromosomal abnormalities.
OBJECTIVE: To measure the intracranial translucency (IT) and the cisterna magna (CM), to produce reference ranges and to examine the interobserver and intraobserver variability of those measurements. To examine the possible association of IT with chromosomal abnormalities. METHODS: Prospective study on pregnancies assessed at 11 to 14 weeks. IT was measured retrospectively in 17 cases with aneuploidy. RESULTS: To produce reference ranges, 465 fetuses were used. IT and CM correlated linearly with crown-rump-length (CRL) and were independent of maternal demographic characteristics and biochemical indices. IT had a weak positive correlation with nuchal translucency. For IT the intraclass correlation coefficient was 0.88 for intraobserver variability and 0.83 for interobserver variability. For CM the intraclass correlation coefficient was 0.95 for intraobserver variability and 0.84 for interobserver variability. The IT multiple of the median was significantly increased in the chromosomally abnormal fetuses (1.02 for the normal and 1.28 for the chromosomally abnormal fetuses, Mann Whitney p < 0.001). IT multiple of the median was a significant predictor of chromosomal abnormality (Receiver Operator Characteristic curve analysis: Area under the curve = 0.86, CI=0.76-0.96, p<0.001). CONCLUSION: Intracranial translucency and CM can be measured reliably at the 11 to 14 weeks examination and the measurements are highly reproducible. IT appears to be increased in fetuses with chromosomal abnormalities.