Midtrimester nuchal thickness and the prediction of postnatal congenital heart defect

The study was performed to determine the sensitivity of nuchal thickness measurements for the detection of congenital heart defects (CHD) and to develop an algorithm for estimating patient-specific risk of CHD.

Nuchal thickness measurements (expressed as multiples of the median) were obtained in 3,003 midtrimester fetuses in which postnatal evaluation of the heart was available. The sensitivity and false-positive rate of nuchal thickness threshold values for detecting CHD were used to calculate the area under the receiver operating characteristics curve. Stepwise logistic regression analysis was used to determine the significant predictors of heart defect among nuchal thickness and epidemiologic risk factors. Individual risk of CHD was calculated on the basis of background population risk of major CHD (estimated at 4.4 of 1,000) and the product of the likelihood ratios of the significant risk factors from the logistic regression.

There were 95 cases of confirmed CHD. Nuchal thickness was statistically significant for the prediction of CHD with an area under the curve = 0.58, P =.01. Nuchal thickness and prior child with CHD were the only significant predictors among the multiple risk factors for this disorder. Patient-specific risk estimates for CHD based on these two "markers" were calculated. It was accurate and improved the prediction of CHD, area under the curve = 0.63, P <.001, compared with nuchal thickness alone.

Midtrimester nuchal thickness measurement significantly detected postnatally confirmed CHD in chromosomally normal fetuses. We report for the first time a method for estimating individual patient risk of CHD.