Davey and Will are also part of a very special group of statistics............
Twins with Down syndrome
Twins or multiple births occur at a rate of about 2% in the population of 15,000 babies with Down syndrome recorded on the UK National Down Syndrome Cytogenetic Register. A total of 244 twin pairs are recorded (some prenatally diagnosed), including 29 pairs (11.8%) where both have Down syndrome. Nine sets of triplets are recorded, each with one affected child. In twin pairs where both have Down syndrome they may not be identical (from one egg), as one pair are a boy and a girl. In a small number of cases, the affected pregnancy was assisted using hormones.
These figures indicate that, in a group of 1000 babies with Down syndrome, some 14 or 15 babies will be a twin or a triplet, with their other twins/triplets unaffected, and 2 or 4 babies will be identical twin pairs, both with Down syndrome.
If we consider all births, we estimate that identical twins with Down syndrome occur at the rate of 1 or 2 in a million pregnancies and non-identical twins at the rate of 14/15 in a million. If the likelihood of having a twin or twins with Down syndrome is also linked to a family history of twins, to age or to assisted pregnancies, we presume these factors will play a part in increasing the risk for some individuals.
National Down Syndrome Cytogenetic Register, Wolfson Institute of Preventive Medicine, St Bartholomew's and the Royal London School of Medicine and Dentistry, website: http://www.mds.qmw.ac.uk/wolfson/ndscr/