World Down Syndrome Day 21st March

It affects around one in every 1,000 babies born. In 2009, just over 700,000 babies were born in England and Wales, and 765 of these were born with Down syndrome.
Background
Screening for Down syndrome and other genetic disorders is offered to all pregnant women. Three different patterns of chromosomes can cause Down Syndrome:

  1. Trisomy 21- 95% of people have three separate copies of chromomosome 21
  2. Robertsonian Translocation- causes 4% have an extra copy of chromosome 21
  3. Mosaicism- 1% with normal and Trisomy cell lines occurs postzygotically

Identifying Patients
Gathering family history information from a patient who has a family history of Down syndrome, and using this information to create a pedigree can assess the likelihood of the condition in the family.  

Consider Sarah and David Everett they are looking to start a family, but are worried as there is a family history of Down syndrome on Sarah’s side of the family.

The diagnostic procedure will be either chorionic villus sampling (CVS) or amniocentesis.CVS Ultrasound Image

Chorionic villus sampling (CVS)

CVS can be carried out earlier than amniocentesis, from around 11 weeks pregnant. It can give the patient an earlier diagnosis if the patient is at risk of having a child with an inherited disorder, such as cystic fibrosis, sickle cell, thalassaemia or muscular dystrophy.