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Nuchal Translucency Predicts Fetal Heart Disease : When screening is added to first-trimester exam, it can pick up defects that otherwise would have been missed.


 

RENO, NEV. — An increased nuchal translucency thickness can predict congenital heart disease in a euploid fetus and indicate pregnancies that should be referred for fetal echocardiography, according to data from the large First and Second Trimester Evaluation of Risk for Aneuploidy study.

When nuchal translucency thickness found on ultrasound in the first trimester is at least 2 multiples of the appropriate gestational median (MoM), the risk of a major congenital heart defect is 14 times higher than normal, Lynn L. Simpson, M.D., said at the annual meeting of the Society for Maternal-Fetal Medicine.

Moreover, as the MoM increased, so did the likelihood of having such a defect: When the MoM was at least 3, the risk was 51 times higher than normal.

Overall, the sensitivity of nuchal translucency screening for major congenital heart defects is low (less than 20%) and therefore is not a good screening test on its own, said Dr. Simpson of the department of obstetrics and gynecology at Columbia University, New York.

However, when nuchal translucency screening is added to the standard first trimester evaluation, it can pick up cases of major congenital heart defects that otherwise would have been missed.

With the cutoff of a nuchal thickness that is at least 2 MoM, about 1% of all infants would end up possibly being referred for fetal echocardiography, Dr. Simpson said.

The First and Second Trimester Evaluation of Risk for Aneuploidy (FASTER) study had 33,968 patients enrolled whose records could be reviewed for cardiac outcome. Among those, there were 195 cases of congenital heart disease (an incidence of 5.7/1,000), of which 43 were defined by the authors as major defects. Major defects were those associated with a poor perinatal outcome or ductal dependency after birth.

The majority of cases of major cardiac defect occurred in fetuses with a nuchal translucency thickness less than the 2 MoM cutoff (81%), hence the low sensitivity of the test. But because the specificity of the test is very high in the absence of aneuploidy, the negative predictive value of the test at the 2 MoM cutoff is greater than 99%, Dr. Simpson said.

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