In 2012, Wellesley et al published data on the number of babies under one year old that had been diagnosed with a chromosome anomaly. They included over two million infants from 11 European countries that were born between 2000 and 2006. The Chromosome 18 Clinical Research Center reached out to the authors of the study to request a breakdown of their data by condition. They kindly provided this information to us. By combining their data with our own, we are able to provide updated estimates for the prevalence of chromosome 18 conditions:
All conditions combined (excluding Trisomy 18): 1 in 20,000
18q-: 1 in 55,000
18p-: 1 in 56,000
Ring 18: 1 in 300,000
One limitation of the Wellesley study was that it only included infants that were diagnosed prenatally or before one year of age. This made it difficult to estimate the actual prevalence of the chromosome 18 conditions because only individuals diagnosed before their first birthday were included. Based on data collected at the Chromosome 18 Clinical Research Center, we know that only about half of chromosome 18 conditions are diagnosed before one year of age. By combining our data with theirs, we eliminated this particular bias in the original data.
It should also be noted that the study authors did not provide data regarding Tetrasomy 18p, so we cannot estimate the prevalence of this condition. However, it is interesting to note that, based on the Research Center's data, only 52% of children with Tet18p born between 2000 and 2006 were diagnosed before their first birthday.
Lastly, based on the data provided by Wellesley, it seems that duplications of 18p and 18q occur in about 1 in 500,000 individuals. However, this is likely an underestimate. In our population, no one with an 18p or 18q duplication were diagnosed before a year of age. Therefore we cannot correct their data with information from our own research.
We hope that families find this updated information interesting. It also shows how collaboration with other institutions and researchers can provide additional information and insight into chromosome 18 conditions!
