The 22-Month and 42-Month Surveys Sweeps focused on exploring the impact of foetal nutrition on early development. Those invited to take part in the 22-Month Sweep were 10 per cent of all study members, all twins and triplets, those born after more than 42 weeks of gestation, and those who had particularly low birthweight. Around 2,500 took part. A similar number, though not the same people, took part in the 42-Month Sweep.
The 22 month sweep covered family circumstances, housing situation, parental smoking, use of childcare, illnesses since birth and a series of tests to measure development including a pencil and paper test where the child was asked to draw a series of simple shapes and a language test where the child was asked to show the examiner different body parts (e.g. hair, hand). The medical examination assessed weight, height, recumbent length, head circumference and other health problems.
The 42 month sweep covered family circumstances, housing situation and a further set of assessments measuring development including making structures using cubes, a vocabulary assessment and drawing shapes. The medical examination assessed height, weight and head circumference.