Ultrasound appearance in Down's syndrome

Typical appearance on ultrasound of a fetus with Down's syndrome are:

• short femur
  
  
• double stomach bubble, as a result of duodenal atresia
  
  
• nuchal oedema - when this occurs at 10-14 weeks gestation this may reflect fetal heart failure (which in turn may reflect a serious anomaly of the heart or great arteries). There is a strong association between chromosomal abnormality and increasing nuchal thickness (fetal nuchal translucency). A study has revealed that, at 10-13 weeks gestation, 84% proven trisomy 21 fetuses had a nuchal translucency of greater than 3 mm - this compares with 4.5% of chromosomally normal fetuses (1)
  
  
• renal pyelectasis
  
  
• sandal gap
  
  
• clinodactyly
  
  
• macroglossia
  
  
• cardiac malformation eg atrioventricular septal defect

Reference:

• Nicholaides K (1994). Br J Obst Gynae, 101, 982.
• Roberts L et al (1994). Prenatal diagnosis. Medicine International, 22(1), 25-8.