The number of live births, Guthrie tests carried out, infants with true (definite and probable) congenital hypothyroidism or transient TSH elevation, and incidence of true congenital hypothyroidism by year is given for period 1 and period 2
| Year | Total live births | No of tests | No with true CH | No with transient TSH elevation | Incidence of true CH |
|---|---|---|---|---|---|
| *Assay problems related to change in TSH antibody used resulted in an increase in the number of babies with a raised TSH on screening that could not be substantiated on confirmatory venous testing. | |||||
| CH, congenital hypothyroidism; TSH, thyroid stimulating hormone. | |||||
| Period 1 | |||||
| 1979 | 68 336 | 10 036 | 5 | 0 | – |
| 1980 | 68 892 | 68 784 | 13 | 0 | 1:5299 |
| 1981 | 69 054 | 69 572 | 18 | 0 | 1:3836 |
| 1982 | 66 196 | 66 864 | 12 | 2 | 1:5516 |
| 1983 | 65 078 | 65 137 | 21 | 3 | 1:3098 |
| 1984 | 65 106 | 65 843 | 15 | 8 | 1:4340 |
| 1985 | 66 676 | 67 338 | 17 | 18* | 1:3922 |
| 1986 | 65 812 | 66 187 | 9 | 11* | 1:7312 |
| 1987 | 66 241 | 67 204 | 19 | 5 | 1:3486 |
| 1988 | 66 212 | 66 975 | 21 | 10 | 1:3152 |
| 1989 | 63 480 | 63 827 | 22 | 7 | 1:2885 |
| 1990 | 65 973 | 66 765 | 21 | 10 | 1:3141 |
| 1991 | 67 024 | 67 374 | 14 | 3 | 1:4787 |
| 1992 | 65 789 | 66 225 | 10 | 5 | 1:6578 |
| 1993 | 63 337 | 63 799 | 17 | 4 | 1:3726 |
| Mean incidence of congenital hypothyroidism 1:4363 live births | |||||
| Period 2 | |||||
| 1994 | 61 656 | 63 479 | 14 | 4 | 1:4404 |
| 1995 | 60 051 | 61 596 | 13 | 2 | 1:4619 |
| 1996 | 59 296 | 60 859 | 13 | 1 | 1:4561 |
| 1997 | 59 440 | 61 407 | 18 | 4 | 1:3302 |
| 1998 | 57 319 | 59 315 | 19 | 4 | 1:3017 |
| 1999 | 55 147 | 56 420 | 13 | 3 | 1:4242 |
| 2000 | 53 076 | 54 490 | 15 | 5 | 1:3538 |
| 2001 | 52 527 | 53 171 | 17 | 3 | 1:3089 |
| 2002 | 51 270 | 52 886 | 19 | 6 | 1:2698 |
| 2003 | 52 432 | 54 473 | 17 | 7 | 1:3084 |
| Mean incidence of congenital hypothyroidism 1:3655 live births | |||||