Characteristics of included studies
| Study: first author (year), location | Cohort population used (if applicable) | No. in analysis | Smoking exposure (prevalence) | Covariates | Decade of birth | Age outcome measured (mean) | Outcome (prevalence) | Overweight | Obesity | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Unadjusted OR (95% CI) | Adjusted OR (95% CI) | Unadjusted OR (95% CI) | Adjusted OR (95% CI) | ||||||||
| Von Kries (1999), Germany | – | 9206 | Maternal smoking in pregnancy (8.01%) | Breastfeeding, high-level parental education, birth weight <2500 g, own bedroom, consumes butter >3×/week | 1997 | 5–6 years | BMI—overweight >90th centile for age and sex (10.7%) and obesity >97th centile for age and sex (3.5%) | 1.51 (1.20 to 1.89) | 1.52 (1.18 to 1.95) | 1.82 (1.28 to 1.58) | 1.85 (1.26 to 2.71) |
| Power (2002), UK Male | 1958 British Cohort | 5113 (9948 total) | Maternal smoking in pregnancy (33.5%) | Maternal BMI, social class, birth weight, infant feeding, social class at age 7 years, physical inactivity, diet, social class | 1958 | 16 years | BMI—‘obesity’ was classified as >90th centile for age and sex. However, these data were included as ‘overweight’ for the meta-analysis. No prevalence available. | 1.29 (1.06 to 1.55) | – | – | – |
| Power (2002), UK Female | 1958 British Cohort | 4835 (9948 total) | Maternal smoking in pregnancy (33.5%) | Maternal BMI, social class, birth weight, infant feeding, social class at age 7 years, physical inactivity, diet, social class | 1958 | 16 years | BMI—‘obesity’ was classified as >90th centile for age and sex. However, these data were included as ‘Overweight’ for the meta-analysis. No prevalence available. | 1.32 (1.12 to 1.65) | – | – | – |
| Von Kries (2002), Germany | – | 6483 | Maternal smoking in pregnancy (8.6%) | High parental education, BMI parent >30, birth weight >90th centile, watching TV >1 hours/day, any breastfeeding, eating snacks while watching TV | 1999–2000 | 5–6 years | BMI: overweight >90th centile for age and sex (no prevalence available); obesity >97th centile for age and sex (no prevalence available) | 1.97 (1.52 to 2.56) | 1.43 (1.07 to 1.90) | 2.96 (1.97 to 4.46) | 2.06 (1.31 to 3.26) |
| Wideroe (2003), Norway and Sweden | – | 336 | Maternal smoking of 1–10 cigarettes/day in pregnancy (31.03%) | Maternal age, maternal skin fold thickness, maternal education, paternal education, duration of breastfeeding, total energy intake in week 17, % fat intake week 33, % carbohydrate intake in week 33, birth weight | 1986–1992 | 5 years | BMI: overweight >85th centile (14.9%) | 2.68 (1.36 to 5.27) | 3.8 (2.0 to 7.2) | – | – |
| Salsberry (2005), USA | National Longitudinal Study of Youths, child–mother file | 3022 | Maternal smoking in pregnancy (26%) | (only unadjusted OR available) | 1982–1996 | 7 years | BMI ‘overweight’ classified as ≥95th centile for age and sex (12%). However, these data were included as obesity for the meta-analysis | – | – | 1.74 (1.32 to 2.29) | – |
| Al Mamum (2006), Australia | Birth Cohort | 3253 | Maternal smoking in pregnancy (36.6%) | Age, sex, socioeconomic position at birth, breastfeeding, consumption of fast food, salad, soft drinks, red meat, TV watching and participation in sport and exercise | 1981–1984 | 14 years | BMI: overweight ≥95th centile for age and sex (CDC reference) (19%); obesity ≥95th centile for age and sex (6/2%) | 1.28 (1.06 to 1.55) | 1.30 (1.05 to 1.61) | 1.36 (1.01 to 1.83) | 1.40 (1.01 to 1.94) |
| Chen (2006), USA Male | CPP: Collaborative Perinatal project | 6181 (12 416 total) | Maternal smoking in pregnancy (51.4%) | Centre, race, socioeconomic position, maternal age at recruitment, prepregnancy BMI, child live birth order, breastfeeding, age of measurement | 1959–1965 | 8 years | BMI: ‘at risk of overweight’ ≥85th centile for age and sex (data included as overweight for meta-analysis); ‘overweight’ ≥95th centile for age and sex (data included as obesity for the meta-analysis). | – | 1.21 (1.05 to 1.39) | – | 1.21 (0.96 to 1.51) |
| Chen (2006), USA Female | CPP: Collaborative Perinatal project | 6235 (12 416 total) | Maternal smoking in pregnancy (51.4%) | Centre, race, Socioeconomic position, maternal age at recruitment, prepregnancy BMI, child live birth order, breastfeeding, age of measurement | 1959–1965 | 8 years | BMI: ‘at risk of overweight’ ≥85th centile for age and sex (data included as overweight for the meta-analysis); ‘overweight’ ≥95th centile for age and sex (data included as obesity for the meta-analysis). | – | 1.37 (1.19 to 1.58) | – | 1.31 (1.06 to 1.51) |
| Dubois (2007), Canada | Quebec longitudinal study of child development 1998–2002 | 1450 | Maternal smoking in pregnancy (25.2%) | Gestational age, birth weight | 1998–2002 | 4.5 years | BMI: ‘overweight’ >95th centile for age and sex (8.5%)(data included as obesity for the meta-analysis) | – | – | 1.6 (1.1 to 2.4) | 1.8 (1.2 to 2.8) |
| Salsberry (2007), USA | – | 3368 | Maternal smoking in pregnancy (27%) | Age of child, gender, age of mother at birth, time trend, height+weight collection method, first born. Socioeconomic factors | 1980–1990 | 12–13 years | ‘Overweight’ as BMI ≥95th centile for age and sex (17%). Data included as obesity in the meta-analysis | – | – | – | 1.36 (1.04 to 1.77) |
| Toschke (2007), Germany | – | 5472 | Maternal smoking in pregnancy (22.8%) | Low educational level of parents, parental obesity, reduced physical activity, watching TV >1 hour/day, no breastfeeding, <5 meals/day | 1995–1996 | 5–6 years | BMI—overweight (11.3%) and obesity (3.2%) as per IOTF definitions | 1.59 (1.32 to 1.91) | 1.32 (1.10 to 1.61) | 2.31 (1.70 to 3.14) | 1.75 (1.25 to 2.43) |
| Mendez (2008), Spain | – | 369 | Maternal smoking in early pregnancy (15.7%) | Child age, gender, breastfeeding duration, maternal age, height, overweight/obesity prior to pregnancy, education, parity, TV watching, child diet | 1997–1998 | 5–7 years | BMI—Overweight as per by IOTF definitions (23.6%) | 2.16 (1.18 to 3.97) | 2.65 (1.26 to 5.54) | – | – |
| Moschonis (2008), Greece | GENESIS: Growth, Exercise and Nutrition Epidemiological Study in preschoolers | 1667 | Maternal smoking in pregnancy (10.5%) | Gender, birth weight, postnatal feeding patterns, birth rank, size at birth, alcohol consumption, parental weight, education of mothers, mothers age | 1998–2002 | 3–5 years | ‘At risk of overweight and overweight’ defined as BMI >85th centile for age+gender (17%) | 1.07 (0.77 to 1.50) | 1.14 (0.76 to 1.90) | – | – |
| Fasting (2009), Norway | PACT: Prevention of Allergy among Children in Trondheim study | 711 | Maternal smoking in early pregnancy (13.6%) | Child gender, maternal education, maternal age, physical exercise, birth weight | 2000–2003 | 4 years | BMI—overweight as per IOTF definitions (10.1%) | 1.25 (0.61 to 2.5) | 1.29 (0.62 to 2.68) | – | – |
| Hawkins (2009), UK | Millennium Cohort Study | 13 188 | Mothers smoking 1–9 cigarettes in pregnancy (11.8%) | Child gender+ethnicity, birth weight, breastfeeding, solids, TV, socioeconomic factors, maternal education, lone mother, household income, community+area factors | 2000–2002 | 3 years | BMI—overweight as per IOTF definitions (23.5%) | 1.17 (1.00 to 1.36) | 1.34 (1.17 to 1.54) | – | – |
| Kleiser (2009), Germany | KiGGs Study | 10 021 | Maternal smoking in pregnancy (16.9%) | Socioeconomic position, migration background, parental overweight, paternal smoking, weight gain in pregnancy, high birth weight, breastfeeding, sleep, media consumption, physical activity, intake of energy food | 1989–2006 | 3–17 years | BMI—overweight (19.7%) and obesity (5%) as per IOTF definitions | 1.65 (1.49 to 1.83) | 1.68 (1.5 to 1.9) | 1.9 (1.6 to 2.26) | 1.37 (1.0 to 1.8) |
| Olson (2009), USA | Basset Mother's Health Project | 321 | Maternal smoking in pregnancy (16.5%) | Maternal BMI, gestational weight gain, birth weight, maternal BMI×birth weight, gestational age, parity, income, gender | 2004–2005 | 4 years | BMI: overweight defined as ≥85th centile for age+sex (32.1%); obesity defined as ≥95th centile for age+sex (14.6%) | 1.92 (1.03 to 3.58) | 1.99 (0.98 to 4.04) | 2.01 (0.87 to 4.60) | 1.86 (0.70 to 4.93) |
| Suzuki (2009), Japan | Project Koshu (formerly Enzan) | 1282 | Maternal smoking in pregnancy (5.5%) | Maternal age, maternal BMI, sleep deprivation, breakfast | 1991–1999 | 9–10 years | BMI—overweight (16.7%) and obesity (4.5%) as per IOTF definitions | 2.22 (1.30 to 3.77) | 1.91 (1.03 to 3.53 | 4.06 (1.96 to 8.42) | 2.56 (1.02 to 6.38) |
| Ajslev (2010), Denmark | Danish National Birth Cohort | 21 121 | Maternal smoking in pregnancy 1–10 cigarettes/day (22.7%) | (only unadjusted OR available) | 1997–2002 | 7 years | BMI—overweight as per IOFT definitions (9.6%) | 1.46 (1.36 to 1.57) | – | – | – |
| Braun (2010), USA | Health outcomes and measures of the environment study | 352 | Maternal smoking in pregnancy (13.6%) | Maternal age, BMI, race and education, marital status, depression, breastfeeding duration, parity, income | 2003–2006 | 2–3 years | Overweight defined as BMI ≥85th centile for age and gender (16.2%) | 2.5 (1.0 to 6.1) | 1.9 (0.6 to 6.1) | – | – |
| Ferreira (2010), Brazil | Nutrition and health of mother-child population of Alagoas Semi-Aridi region | 716 | Maternal smoking in pregnancy (20.4%) | (only unadjusted OR available) | 2002–2006 | 1–5 years | Overweight defined as children with weight for height >2 SD (6.3%) | 1.8 (0.9 to 3.5) | – | – | – |
| Kuhle (2010), Canada | CLASS: Children's lifestyle and school performance study | 3351 | Maternal smoking in pregnancy, 0–0.5 packs of cigarettes/day (26%) | Prepregnancy weight, parity, physical activity, sedentary activity, weight for gestational age | 1991–1992 | 11–12 years | BMI—overweight as per IOFT definitions (33%) | – | 1.39 (1.14 to 1.70) | – | – |
| Mangio (2010), Sweden | – | 8621 | Maternal smoking in pregnancy (10.2%) | Year, gender, maternal education, parents country of birth, crowded living, first born, parental education programme and economic stress), parental overweight, child intake of sweetened beverages | 1999–2004 | 4 years | BMI—overweight (15%) and obesity (3%) as per IOTF definitions | 1.48 (1.24 to 1.77) | 1.48 (1.17 to 1.87) | 2.29 (1.68 to 3.13) | 2.1 (1.37 to 3.23) |
| Pinot de Moira (2010), UK | 1958 British Birth Cohort: Offspring data | 1889 | Maternal smoking in pregnancy (24.1%) | Gender, age, parental BMI, birth weight, gestational age, breastfeeding, social class | 1982–1987 | 4–9 years (6.9 years) | BMI—overweight (29.9%) and obesity (6.8%) as per IOFT definitions | – | 1.02 (0.71 to 1.47) | – | – |
| Seach (2010), Australia | MACS: Melbourne Atopy Cohort Study | 307 | Maternal smoking in pregnancy (5.6%) | Breastfeeding, paternal smoking, socioeconomic status, childcare attendance, birth weight | 1990–1994 | 10 years | BMI—overweight (25.1%) and obesity (2.6%) as per IOFT definitions | – | 1.65 (0.53 to 5.11) | – | – |
| Gorog (2011), Central Europe | CESAR: Central European Study on Air pollution % Respiratory health | 8926 | Maternal smoking in pregnancy (12.5%) | Breastfeeding, <1 person/room winter fruit, exercise, mothers education, fathers education, high birth weight, summer fruit, mothers occupation, study area | – | 9–12 years | BMI—overweight (14.3%) and obesity (2.7%) as per IOFT definitions | 1.2 (0.94 to 1.52) | 1.26 (1.03 to 1.55) | 1.69 (0.87 to 3.27) | 1.82 (0.95 to 3.5) |
| Raum (2011), Germany | – | 1954 | Maternal smoking in pregnancy (16.5%) | Parity, birth weight, breastfeeding, TV, sports, visits to fast food restaurants, parental education, maternal BMI, age of mother, smoking at other times | 1995–1996 | 6 years (5.8 years) | BMI—overweight (8.9%) as ≥90th centile and obesity (4.2%) as ≥97th centile for age and gender | 1.83 (1.27 to 2.63) | 0.89 (0.51 to 1.55) | – | – |
| Laitinen (2012), Finland | Northern Finland 1986 Birth Cohort | 6637 | Maternal smoking in pregnancy, 1–10 cigarettes/day in pregnancy (8.3%) | Gender, parity, maternal prepregnancy BMI, level of haemoglobin in early pregnancy, smoking in early pregnancy, level of education | 1986 | 16 years | BMI—overweight as per IOFT definitions (14.8%) | 1.39 (1.11 to 1.75) | 1.36 (1.04 to 1.77) | – | – |
| Messiah (2012), USA | NHANES: National Health and Nutrition Examination survey | 3644 | Maternal smoking in pregnancy (17%) | Age, gender, family poverty/income ratio, year of survey, mothers age at birth, race. | 1999–2008 | 3–6 years | Overweight (26.5%) defined as ≥85th centile and obesity (13.8%) defined as ≥95th centile for age and gender | 1.27 (0.98 to 1.64) | 1.64 (1.16 to 2.30) | 1.54 (1.15 to 2.06) | 1.97 (1.34 to 2.89) |
| Risvas (2012), Greece | GRECO: Greek Childhood Obesity study | 2093 | Maternal smoking in pregnancy, 1–9 cigarettes/day at conception (38.7%) | Child age, gender, physical activity status, quality of diet, mothers age at pregnancy, mothers BMI pre-conception, mothers % BMI change, smoking habits at conception and gestation | 1996–1997 | 10–12 years (10.8 years) | BMI—overweight (42%) and obesity (13.8%) as per IOFT definitions | 1.28 (0.99 to 1.65) | 1.32 (0.99 to 1.77) | – | – |
| Harris (2013), USA | Nurses Health Study II | 35 370 | Any maternal smoking in pregnancy (26.1%) | Age, maternal/paternal/prenatal factors, parental smoking, birth weight, body size in childhood | 1989 | 18 years | BMI: overweight BMI >25 (no prevalence available); obesity BMI >30 (no prevalence available) | 0.94 (0.75 to 1.17) | 1.27 (1.12 to 1.43) | 1.36 (1.16 to 1.58) | 1.35 (1.08 to 1.68) |
| Shi (2013), Canada | – | 968 | Maternal smoking in pregnancy (17%) | age, sex, ethnicity, bf experience, physical activity, birth weight | 2007–2009 | 6–11 years (8.6 years) | BMI Z scores: overweight Z Score 1–2 SDs above mean (21%); obesity Z Score >2 SDs above mean (13%) | 1.82 (0.82 to 4.06) | 2.25 (0.98 to 5.15) | 2.26 (1.18 to 4.31) | 2.41 (1.33 to 4.36) |
| Yang (2013), Belarus | PROBIT trial | 12 192 | Maternal smoking in pregnancy (18%) | Cluster, child sex and age at outcome measure | 1996–1997 | 6.5 years | BMI: overweight BMI >95th centile (prevalence not available) (CDC cut-offs) | – | 1.05 (0.63 to 1.75) | – | – |
| Anderson (2014), Hawaii | Special supplemental nutritional programme for Women, Infants and Children (WIC) data | 15 106 | Maternal smoking in pregnancy (7.9%) | NA | 2005–2009 | 2 years | BMI: overweight BMI 85th–95th centile (CDC cut-off) (12.5%); obesity BMI >95th centile (8.5%) | 1.06 (0.88 to 1.27) | – | 1.49 (1.23 to 1.80) | – |
| Bammann (2014), Europe | IDEFICS | 1024 | Maternal smoking in pregnancy (16.9%) | Sex, age, country, gestational weight gain, caesarean section, breastfeeding at 4–11 months, early introduction solids, maternal and paternal BMI, parental educational level | 2007–2008 | 4–8 years | BMI –obesity as per IOFT definitions (no prevalence as case–control trial) | – | – | 1.52 (1.16 to 1.98) | 1.43 (0.94 to 2.16) |
| Grazuleviciene (2014), Lithuania | KANC cohort PHENOTYPE project | 1489 | Maternal smoking in pregnancy (12.7%) | NA | 2007–2009 | 4–6 years | BMI—overweight as per IOFT definitions (7.5%) | 2.42 (1.38 to 4.21) | – | – | – |
| Moller (2014), Denmark | Danish National birth cohort | 32 747 | Maternal smoking in pregnancy (23.4%) | Sex, parity, BWT, maternal gestational weight gain, maternal age, prepregnancy BMI, paternal smoking, socioeconomic position | 1996–2002 | 7 years | BMI—overweight as per IOFT definitions (9.4%) | – | 1.31 (1.15 to 1.48) | – | – |
| Suzuki (2014), Japan | Project Koshu (formerly Enzan) | 2230 | Maternal smoking in pregnancy (24.9%) | NA | 1991–2006 | 3 years | BMI—overweight as per IOFT definitions (no prevalence) | 1.20 (0.81 to 1.77) | – | – | – |
| Timmermans (2014), Netherlands | KOALA birth cohort study | 398 | Maternal smoking in pregnancy (7.9%) | Gender, recruitment group, maternal age at pregnancy, maternal BMI, prepregnancy age and smoking interaction | 2000 | 6–7 years | BMI: overweight BMI >85th centile for age and sex (9.5%) | 3.65 (1.44 to 9.25 | 3.72 (1.33 to 10.4) | – | – |
| Wen (2014), Australia | Health Beginnings trial | 242 | Maternal smoking in pregnancy (12%) | NA | 2007–2010 | 2 years | BMI—overweight as per IOFT definitions (14%) | 1.1 (0.35 to 3.43) | – | – | – |