Table 1 Potential risk factors, sweep of data collection and factor level of analysis
VariableSweep of data collection*Units of analysis
BirthweightFirstz-score adjusted for gestational age and gender
Child’s genderFirstMale or female
Child’s ethnicityFirstWhite; mixed; Indian; Pakistani; Bangladeshi; black; other
Breastfeeding durationFirstNever breastfed; breastfed for <17.4 weeks; breastfed for ⩾17.4 weeks
Introduction of solid foodsFirstWeeks: <17.4 or ⩾17.4
Television viewingSecondDaily hours: <1; ⩾1 and <3; ⩾3
Maternal socioeconomic circumstancesFirstManagerial and professional; intermediate; small employers and own account; lower supervisory and technical; semi-routine and routine; never worked and long-term unemployed
Maternal highest academic qualificationFirstDegree (highest); diploma in higher education; A/AS/S levels; O level/GCSE grades A–C; GCSE grades D–G; other; none (lowest)
Lone motherhood statusFirstNon-lone mother or lone mother
Age at first live birthFirstYears: 14–19; 20–24; 25–29; 30–34; 35+
Age at MCS birthFirstYears: 14–19; 20–24; 25–29; 30–34; 35+
ParityFirstCohort child first live born (nulliparous) or not first live born (multiparous)
Number of children in the household (including cohort child)Second1; 2 or 3; 4 or more
Household incomeSecond†Per annum: £0–11 000; £11 000–22 000; £22 000–33 000; £33 000+
Maternal smoking during pregnancy (at 3 months’ gestation)FirstDaily: none, 1–9, 10–19, 20+
Parental overweight when cohort child was aged 9 monthsFirstBMI (kg/m2): Both parents <25; mother only ⩾25; father only ⩾25; both parents ⩾25
Maternal prepregnancy overweightFirstYes (BMI ⩾25 kg/m2) or no (BMI <25 kg/m2)
Maternal employment‡First and secondHours worked per week: never worked; 1–20; 21+
Whether child has meals at regular timesSecondAlways, usually, never or sometimes
Easy access to food shops and supermarketsFirstHow common: very, fairly, not very, not at all
Neighbourhood conditions: noisy neighbours, rubbish, vandalism, pollution§FirstHow common: very, fairly, not very, not at all
Satisfaction with area where family livesFirstVery satisfied, fairly satisfied, neither satisfied nor dissatisfied, fairly dissatisfied, very dissatisfied
Whether there are any places where children can play safelyFirstYes or no
Access to a gardenFirstYes or no
CountryFirstEngland, Wales, Scotland, Northern Ireland
Ward typeFirstAdvantaged, disadvantaged, ethnic
  • *Children were aged approximately 9 months at the first contact and 3 years at the second contact.

  • †Values from the second contact were used unless missing; values from the first were substituted.

  • ‡Average hours worked per week during the weeks worked from birth to the second contact.

  • §A composite of neighbourhood conditions based on how common the following were: noisy neighbours or loud parties; rubbish or litter lying around; vandalism and deliberate damage to property; pollution, grime or other environmental problems.