Table 1

Ascertainment problems and incidence of severe disability at 2 years

Follow up	Babies born in 1983	Babies born in 1990-1	Percentage with severe disability (95% confidence interval)
Child reviewed without difficulty at 2 years	9/204	40/505	6.9 (5.2 to 9.0)
Child only traced with difficulty because of family mobility, etc	3/14	4/26	17.5 (7.3 to 32.8)
Assessment only arranged with difficulty after the child was traced^1-150	6/12	20/35	55.3 (40.1 to 69.8)
Died after discharge from hospital but before the age of 2	1^1-151/6	7^1-151/16	36.4 (17.2 to 59.3)
Total	19/236	71/582	11.0 (8.8 to 13.1)

↵1-150 Family mobility also added to the difficulty of maintaining contact with seven of these 47 families.
↵1-151 Judged likely to become disabled by two years because of cerebral ultrasound and autopsy findings, and/or post-neonatal neurological symptoms.