Table 2 Summary data extracted from studies of childhood overweight ordered by year of birth of study children
Author Year of publication Study designYear of birth of study children Sample population Setting/data source % single mothersMaternal employment measure (prevalence %) and comparatorHealth indicatorUnadjusted OR (95% CI)* (OR>1 indicates poorer health outcome)Adjusted OR (95% CI) (OR>1 indicates poorer health outcome)Variables included in adjusted analysisQuality rating†
Anderson232003Cohort1975–1993††Mothers and their children (n = 16650) aged 3–11 yearsNational Longitudinal Survey of Youth, USA27.9%a) Mother worked ⩾35 hours per week (prevalence not stated) vs never workedb) Mother worked <35 hours per week (prevalence not stated) vs never workedc) Employment intensity: average hours worked per week if working since child’s birth (units of 10 hours)d) Employment duration: number of weeks mother employed since child’s birth (units of 52 weeks)Child overweight: BMI >95th percentile of CDC growth chartsa) 1.43(CI not calculable)¶b) 1.08(CI not calculable)¶c) No unadjusted analysis d) No unadjusted analysisa) No adjusted analysisb) No adjusted analysisc) Probit estimates: mothers who work 10 hours more per week increase the likelihood that their children will be overweight by 1.2 percentage pointsStratification by maternal education: estimated increase in childhood overweight per extra 10 hours worked is greater for children of more educated than less educated mothersd) Probit estimates: number of weeks of maternal employment not significantly associated with childhood overweighta) N/Ab) N/Ac) Block 1§Stratification by maternal educaton:Blocks 1, 2 and 3§d) Blocks 1 and 2§II AAA
Takahashi421999Cohort1989Children (obese, n = 427; non-obese, n = 854) aged 3 yearsToyama prefecture, JapanN/RMother’s job, full-time (34.6%) vs not full-timeChild obesity: BMI ⩾181.33 (p<0.05)No significant association (OR not reported)Obesity of mother and father. Child’s physical activity/weight at birth/duration of outdoor playtime/snacking regularity/meal times/BMI at birth/snacking frequency/sleeping time/bedtime/wake-up time/kindergarten attendance/seasoning of food. Caretaker status.II AAA
Melgar-Quinonez432004Cross-sectional1993–95Families (n = 238) with a child aged 3–5 years, of low income and Mexican American ethnic originCalifornia, USAN/RMother employed outside the household [41%] vs not employed outside the householdChild overweight (BMI ⩾85th percentile of CDC growth charts) or obesity (BMI ⩾95th percentile)No significant association (OR not reported)Adjusted analysis does not include maternal employment variableN/AII AA
The following paper comprised cross-sectional and case-control elements
Lamerz282005Cross-sectional1995–96Parents of children (n = 1979) aged 5–7 yearsAachen, Germany11%a) Maternal employment, full-time (8.9%) vs noneb) Maternal employment, part-time (39.4%) vs nonec) Maternal employment, full or part-time (48.3%) vs noned) Maternal employment, full-time vs part-timeChild obesity: BMI ⩾90th percentile for German childrena) 0.75 (0.41 to 1.37)¶b) 0.62 (0.43 to 0.88)¶c) 0.64 (0.46 to 0.89¶d) 1.21 (0.64 to 2.30)¶a) 0.92 (0.49 to 1.75)b) 0.82 (CI not calculable)c) No data availabled) 1.12 (0.58 to 2.17)Education/BMI of mother and father. Father’s employment. Living space per person (m2). Single parent. GenderIII AAA
Lamerz282005Case-control1995–96Children (obese, n  = 146; non-obese, n = 221) aged 5–7 yearsAachen, Germany11%a) Maternal employment (55.2%) vs noneb) Working more than 4 hours per day (25.4%) vs nonec) Working >0–4 hours per day (28.6%) vs noned) Working more than 4 hours per day vs >0–4 hours per daye) Working at weekends (19.4%) vs not workingChild obesity (cases  =  BMI ⩾85th percentile for German children; controls  =  BMI 40th to 60th percentile for German children)a) 0.60 (0.38 to 0.94)¶b) 0.78 (0.45 to 1.35)¶c) 0.47 (0.27 to 0.81)¶d) 1.66 (0.88 to 3.10)¶e) 0.79 (0.44 to 1.41)¶a) No significant association (OR not reported)b) No significant association (OR not reported)c) No significant association (OR not reported)d) No significant association (OR not reported)e) No significant association (OR not reported)Education/type of occupation of mother and father. Father’s employment/hours of work/hours of work at weekends. Household net incomeIII AAA
Hawkins242007cohort2000–02Children (n = 13113) aged 3 yearsMillennium Cohort Study, UK14%a) Maternal employment, any since child’s birth(58.2%) vs noneb) Hours worked per week, per 10 hoursc) Duration of employment, per 1 yearChild overweight, including obesity, as defined by IOTF cut-offs for BMIa) 1.07 (0.97 to 1.18)b) 1.06 (1.02 to 1.09)c) 1.03 (0.99 to 1.07)a) 1.15 (1.02 to 1.29)b) 1.12 (1.06 to 1.18)c) 0.97 (0.91 to 1.04)Birth weight.Maternal ethnic group/highest academic qualification/age at first live birth/lone motherhood status/pre-pregnancy body size/smoking during pregnancy**II AAA
Kasemsup292006Cross-sectional<2003††Mothers of overweight (n = 35) or normal weight (n = 45) children aged 3–5 years, of Hmong ethnic originMinneapolis/St Paul metropolitan area, USAN/RMother employed part- or full-time (48%) vs not employedChild overweight: BMI ⩾95th percentile of growth charts2.50 (0.98 to 6.37)¶No adjusted analysisN/AI A
  • BMI, body mass index; CDC, Centers for Disease Control and Prevention; CI, confidence intervals; IOTF, International Obesity Task Force; N/A, not applicable; N/R, not recorded; OR, odds ratio.

  • *95% confidence intervals, unless otherwise stated.

  • †III  =  strong internal validity (four or more domains strong or three domains strong and none weak); I  =  weak internal validity (three or more domains weak); II  =  moderate internal validity (those not fulfilling criteria for strong or weak). AAA  =  findings likely to be applicable across a broad range of populations and settings (but may need appropriate adaptation); AA  =  findings applicable only to populations and settings included in the study – success of broader application is uncertain; A  =  applicable only to populations and settings included in the study.

  • ‡Estimated year of birth of study children.

  • ¶Odds ratio calculated by review authors using data derived from the published paper.

  • §Block 1 variables  =  average hours worked per week if working since child’s birth, number of weeks worked since child’s birth, mother reported height and weight; Block 2 variables  =  Black non-Hispanic, Hispanic, mother’s education, child was first born, number of children, child’s birthweight, child’s and mother’s age in years, year of survey, education levels of the mother’s parents, whether mother’s parents were present when she was 14, whether the child is female; Block 3 variables  =  child was breastfed, mother’s BMI, average family income since birth, child’s life mother was married.

  • **Employment measures b) and c) additionally adjusted for employment [maternal hours worked and duration, partner hours worked and duration].