azurefields
Taken from this article:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4319261/
Excerpt:
"The overall incidence of CH ranges from 1 in 3000 to 1 in 4000 newborn infants.[7,8] The incidence of CH is higher in Hispanic and Asian individuals and lower in black individuals.[8] There is a 2:1 greater incidence in females compared with males and there is an increased risk in infants with Down's syndrome. In India, the prevalence has been reported to be 1 in 2640 in screening 40,000 newborn.[9] In 2007, Harris and Pass reported that the incidence (birth prevalence) of CH detected by newborn screening programs in the United States had nearly doubled over the previous two decades, increasing from 1:3985 (in 1987) to 1:2273 (in 2002).[10] Over the years described above, there has been a 37% increase in Asian births and a 53% increase in Hispanic births in the United States.[11] The exact cause of this increase in incidence is not known but factors that may be implicated include changes in screening methods (lower TSH cutoff), obtaining the screening specimen earlier (closer to the TSH surge after birth) [Table 1]."
So, in this article it's 1 in 3,000 o 4,000 in the US and 1 in 2650 in India.
Also:
"Harris and Pass reported that the incidence (birth prevalence) of CH detected by newborn screening programs in the United States had nearly doubled over the previous two decades, increasing from 1:3985 (in 1987) to 1:2273 (in 2002).[10]"
Is it possible the incidence of CH in the US has doubled over the past two decades are increase in fluoridation of water?