Ultrasound Misses Numerous Heart Defects in Fetuses

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Based on research conducted at Linköping University in Sweden, one reason why malformations are not detected is obesity in the expectant mother. Moreover, six out of ten grave heart defects in fetuses go unnoticed in the ultrasound scans administered to all pregnant women.

On an annual basis 2,000 children are born in Sweden with serious malformations, of which almost half are heart defects. Detecting these during the first stage of pregnancy is a significant challenge for prenatal healthcare.

"The lives of children born with serious heart defects are in constant danger; some of them need immediate operations or medical treatment. If these defects are detected during the pregnancy the babies can be born in Lund or Gothenburg where the hospital has facilities for child heart surgery," explains senior physician at the Linköping University Hospital Women's Clinic and also a graduate student in obstetrics and gynaecology at Linköping University, Eric Hildebrand.

The root of his study is an examination of over 21,000 ultrasound scans in the south-east healthcare region in Sweden, covering the counties of Jönköping, Kalmar, and Östergötland.

In this region all expecting mothers are offered two ultrasound scans, the first in weeks 11-14, and the second in weeks 18-20. In the first scan the midwife dates the pregnancy, searches for the possibility of twins and carries out a general examination of the anatomy of the embryo. In the second scan the organs are screened for malformations.

In the examination the results of the two scans are compared. Unsurprisingly, considerably fewer malformations are revelaed in the first scan. It was especially difficult to detect heart defects. During the eleventh to the fourteenth weeks no defects were found at all, yet in the eighteenth to twentieth week, 37% of serious defects were discovered.

One reason for missing malformations is that the ultrasound image is affected by the body of the mother. For instance diagnosis is made more difficult by obesity-a BMI over 30-which is the case for 13% of the mothers.

"Subcutaneous fat detracts from the quality of the image, making it more difficult for us to see malformations," said Hildebrand.

The statistics also reveal that obesity itself raises the risk of conditions like spina bifida, although the increased risk for the individual is small. That makes it doubly important to be able to provide strong embryo diagnostics for the expectant mother.

In the case of chromosome abnormalities, a thorough examination of the national medical birth register of children born between 1995 and 2010 showed that one in 700 children was born with Downs syndrome. A certain connection with obesity was also seen.

Hildebrand suggests a couple of important measures for a more trustworthy embryo diagnostic that came out of the in the studies:

-The methods of detecting heart defects need to be improved. One way is to give midwives additional education and training in interpreting heart images, including with what is known as color Doppler for blood flow in the heart.

-The best diagnostic tool for Downs Syndrome is the CUB, or Combined Ultrasound and Biochemical screening test, which works just as well regardless of whether the mother is obese or not.