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Table 1 Characteristics of studies included in the systematic review and meta-analysis

From: Gestational weight gain and offspring’s cognitive skills: a systematic review and meta-analysis

Study Country Studu design Years of recruitment n mothers Mother’s age (i) GWG classification n offspring Offspring’s age (i) Measuring tools and cognitive domains Adjustement variables
Gage et al. 2013 [38] UK Cohort 1991–1992 8653 28.52 (4.75) IOM 2009 5836
5191
7339
4
8
16
School entry assessment score.
Wechsler Intelligence Scale for Children:
- → Standarized IQ.
School scores.
Maternal’s variables: age, gestational age, parity, education, pregestational BMI, tobacco consumption and type of delivery.
Offspring’s variables: sex, age at evaluation.
Hinkle et al. 2016 [13] Norway and Sweden Cohort 1986–1988 344 29.1 (4.2) IOM 2009 552 5.2 (0.2) Wechsler Preschoolers and Primary Scales of Intelligence (WPPSI-R), Full Scale:
- → Verbal IQ.
- → Performance IQ.
- → Full scale IQ.
Maternal’s variables: age, parity, education, IQ, socioeconomic status, civil status, pregestational BIM, prepregnancy diseases, smoking and alcohol use, nausea and vomiting during pregnancy.
Offspring’s variables: sex, age at IQ assessment.
Sensitive analysis limited to full-term birth.
Huang et al. 2014 [9] USA Cohort 1959–1976 29,942 21.3 (8.4) IOM 2009 8059 children with siblings.
22,513 children with no siblings.
7.1 (0.8) Stanford–Binet intelligence scale and Graham–Ernhart Block Sort test.
Wechsler Intelligence Scale for Children (WISC I):
- → Verbal IQ
- → Performance IQ
- → Full scale IQ.
Maternal’s variables: age, race, education, civil status, socioeconomic status, parity, smoking in pregnancy and hospital.
Keim et al. 2012 [14] USA Cohort 1959–1973 31,968 < 20: 20.3%
20–29: 64.4%
30–34: 11.3%
> 35: 4%
IOM 2009 8704 children with siblings.
23,264 children with no siblings.
4
4
7
7
Stanford–Binet intelligence scale
Graham–Ernhart Block Sort test.
Wechsler Intelligence Scale for Children.
Wide Range Achievement Test (WRAT):
- → Spelling
- → Arithmetic
Maternal’s variables: age, race, parity, socioeconomic status, and smoking.
Offspring’s variables: sex and siblings.
Kominiarek et al. 2018 [39] USA Cohort 2006–2009 948 27.95 (6.56) IOM 2009 948 3
5
Differential Ability Scale-II.
Wechsler Preschool and Primary Scale of Intelligence.
Maternal’s variables: race–ethnicity and education.
Offspring’s variables: sex.
Li et al. 2018 [15] China Cohort 2002–2006 1744 NR IOM 2009 1307 8.78 (0.82) Wechsler intelligence scale for children (WISC-IV) Maternal’s variables: parental age, gestational age, county, education, parents’ job, household wealth index, child school level, prenatal micronutrient supplementation, prepregnancy BMI.
Offspring’s variables: age, sex, older siblings birth weight
Naeye et al. 1981 [12] USA Cohort 1959–1966 2183 NA Own criteria (ii) 2183 0.67
4
Bayley score.
IQ.
Stratified by race, gestational age at birth, socioeconomic index (including education, work and family income).
Neggers et al. 2003 [16] USA Cohort 1991–1993 355 21.6 (7.3) IOM 1990 355 5.3 (0.3) Differential Ability Scales (DAS):
- → IQ
- → Verbal
- → No verbal ability,
Peabody gross motor scales (PPVT):
- → Reflexes,
- → Balance
- → Locomotors reflexes.
Peabody Picture Vocabulary Test (PPVT):
- → Language skills.
Maternal’s variables: age, gestational age, mother’s PPVT, tobacco use and maternal alcohol intake and zinc supplementation.
Offspring’s variables: Offspring’s age, birth weight, home environment and childcare.
Pugh et al. 2015 [40] USA Cohort 1983–1986 530 NA Own criteria (iii) 530 10 Stanford-Binet Intelligence Scale:
- → IQ.
Wisconsin Card Sorting Test and Trail Making test:
- → Cognitive flexibility.
Maternal’s variables: race, parity, intelligence, socioeconomic status, education, job, civil status, depressive symptoms and preconception substance use.
Offspring’s variables: sex and home environment.
Pugh et al. 2016 [35] USA Cohort 1983–1986 574 NA Own criteria (iii) 542 6 and 10
14
Wide Range Achievement Test-Revised (WRAT-R)
- → Math.
- → Reading.
- → Spelling
Wechsler Individual Achievement Test (WIAT):
- → Math.
- → Reading.
- → Spelling
Maternal’s variables: race, parity, job, intelligence, socioeconomic status, depression and pregestational BMI.
Offspring’s variables: sex and home environment.
Tanda et al. 2013 [17] USA Cohort 1978 3412 25.4 (5) IOM 2009 3412 5.96 (0.64) Peabody individual achievement test (PIAT):
- → Math.
- → Reading.
Offspring’s variables: age and siblings.
Tavris et al. 1982 [36] USA Cohort 1959–1966 2443 NA Own criteria (iv) 1638 5 Raven Coloured Progressive” matrices test:
- → Intelligence.
Confounding variables without adjusting for them: maternal age, race, parity, maternal education, weight/height ratio, time since the last gestation, parental education and socioeconomic status.
Widen et al. 2018 [37] USA Cohort 1959–1966 2084 28.4 (5.9) NR 1825 9–11 Raven Coloured Progressive” matrices test:
- → Intelligence.
Peabody Picture Vocabulary Test (PPVT):
- → Language skills.
Maternal’s variables: race, age, parity, socioeconomic status, education, peabody IQ score and pregestational BMI.
Offspring’s variables: birth weight and size.
  1. (i) As reported by the original studies in years: intervals, age in whole years at which the measurement was made or average with its standard deviation in years. (ii) Naeye own criteria: suitable GWG 22–32 pounds. (iii) Pugh own criteria 2015 and 2016: suitable GWG was between − 1 to + 1 SD. (iv) Tavris own criteria: suitable GWG 5–29 pounds
  2. IOM Institute of Medicine of the United States, GWG gestational weight gain, BMI body max index, IQ intelligence quotient, NA not available, USA United States of America, UK United Kingdom