Here is a list of useful datasets in the UK
Avon Longitudinal Study of Parents and Children (ALSPAC)
ALSPAC consists of 14,000 mothers enrolled in ALSPAC during pregnancy in 1991 and 1992, and their children. Data collection has focussed on health and development topics from birth up to age 17 years and includes biological samples.
British Cohort Study (BCS70)
The BCS70 comprises data referring to all children born in Great Britain in one week in 1970, for whom data were collected at birth and again in seven further sweeps at ages 6, 10, 16, 26, 30, 34 and 38. The original cohort consisted of around 17 000 children.
Growing up in Scotland (GUS)
Growing Up in Scotland is a longitudinal study that is following the lives of three cohorts of children in Scotland from the early years, through childhood. GUS provides information to support policy making and is also a broader resource for other interested parties. The first birth cohort has five completed sweeps of data available to age 5, with age 6 data being collected.
Millennium Cohort Study
The Millennium Cohort Study (MCS) is a longitudinal dataset following the lives of babies born in 2000-2001. The original sample containing babies born in all 4 countries of the UK, was obtained from approximately 18,500 families. Completed data collection sweeps with data available for analysis relate to when the child was age 9 months, 3 years, 5 years and 7 years. Plans and development for a further sweep are in place for age 11.
National Child Development Study (NCDS)
NCDS comprises data referring to all children born in Great Britain in one week in 1958, which were collected at birth and then in eight further surveys at ages 7, 11, 16, 23, 33, 42, 46 and 50. The original cohort consisted of around 17 000 children.