Certain second trimester markers for Down’s syndrome that are identified in an ultrasound are more significant than others.

The finding came from new research published in the journal Ultrasound in Obstetrics & Gynecology. The results of this investigation will help modify pregnant women’s risks for having a baby with the chromosomal disorder.

Every pregnant woman is asked whether she would like screening for Down’s syndrome, who begin with a background risk based on how old they are.

There are specific characteristics identified during an ultrasound exam in the second trimester of a woman’s pregnancy that are possible indicators for Down’s syndrome.

The potential markers include:

  • absent or small nose bone
  • dilated brain ventricles
  • mild kidney swelling
  • bright spots in the heart
  • ‘bright’ bowels
  • shortening of an arm bone or thigh bone
  • an abnormal artery to the upper extremities
  • increased thickness of the back of the neck

Kypros Nicolaides, MD, of the Harris Birthright Research Centre for Fetal Medicine at King’s College London in England, and team set out to examine how these markers influence risk.

They looked at all research published between 1995 and 2012 that demonstrated results on markers for Down’s syndrome detected during the second trimester of pregnancies.

After finding 48 reports, they determined that the most single markers have only a little impact on altering the likelihood for Down’s syndrome.

The authors explained:

“This finding could have important clinical implications because currently in the United States, when a marker such as a short arm or thigh bone is detected, women are told that they are at high risk of having a child with Down’s syndrome.”

The researchers, however, did find some markers that indicate increased risks.

The risk increases three to four times when the following are detected:

  • increased thickness of the back of the neck
  • dilated brain ventricles
  • an abnormal artery to the upper extremities

The risk increases six or seven times when there is an absent or small nose bone identified. “The detection of any one of the findings during the scan should prompt the sonographer to look for all other markers or abnormalities,” said Prof. Nicolaides

The research also demonstrated that the risk of having a child with Down’s syndrome is reduced seven times if a comprehensive ultrasound exam during the second trimester shows that all major markers are nonexistent.

The results demonstrate that the relative significance of ultrasound markers is very different to what scientists have believed in the past.

The findings from this report will be included in obstetric ultrasound scan software that alters women’s risks for giving birth to a baby affected by Down’s syndrome, Professor Nicolaides concluded.

Written by Sarah Glynn