Table 1.

Characteristics of the included studies

	Study	Setting	Primary study design	Study population	N (data on child development)	Child development tool used	Child age in years at assessment (mean±SD)
Asia
1	Black (2004)19	Bangladesh	Randomised controlled trial	Birth cohort	221	Bayley Scales of Infant and Toddler Development, 2nd edition (BSID-II) and the Home Observation for Measurement of the Environment (HOME) Inventory	1.06±0.03
2	Tofail (2008)20	Bangladesh	Randomised controlled trial	Birth cohort	2853 total (2116 tested)	Two problem-solving tests, motor index of Bayley Scales of Infant and Toddler Development, 2nd edition (BSID-II) and Wolke’s behaviour ratings	0.61±0.02
3	Tofail (2012)21	Bangladesh	Randomised controlled trial	Prospective, community-based cohort	249	Bayley Scales of Infant and Toddler Development, 2nd edition (BSID-II)	0.84±0.01
4	Taneja (2005)22	India	Randomised placebo-controlled trial	Prospective, community-based cohort	571	Bayley Scales of Infant and Toddler Development, 2nd edition (BSID-II)	1.25±0.16
5	Kvestad (2015)23	India	Randomised placebo-controlled trial	Prospective, community-based cohort	422	Ages and Stages Questionnaire, 3rd edition (ASQ-3)	1.37±0.60
6	Yousafzai (2014)24	Pakistan	Community-based cluster-randomised effectiveness trial	Prospective, community-based cohort	1357	Bayley Scales of Infant and Toddler Development, 3rd edition (BSID-III)	11.6±0.83
7	Duazo (2010)25	Philippines	Longitudinal programme evaluation	Birth cohort	4904	Philippines Revised Early Childhood Development Checklist (REC)	1.62±0.88
8	Villegas (2007)26	Thailand	Randomised controlled trial	Prospective, facility-based cohort	503	Shoklo Developmental Test	1.62±0.02
Sub-Saharan Africa
9	Shapiro (2013)27	Botswana	Randomised controlled trial	Prospective, community-based cohort	224	Bayley Scales of Infant and Toddler Development, 3rd edition (BSID-III)	2.03±0.08
10	Bogale (2009)28	Ethiopia	Cross-sectional study	Cross-sectional, community-based cohort	100	Raven's Coloured Progressive Matrices (CPM) and Kaufman Assessment Battery for Children-II (KABC-II)	5.11±0.24
11	Gladstone (2011)29	Malawi	Cross-sectional community-based cohort study	Community-based cohort	840	Ten Question Questionnaire (TQQ) and Malawi Developmental Assessment Tool (MDAT)	1.74±0.33
12	McDonald (2013)30	Tanzania	Randomised placebo-controlled trial	Birth cohort	305	Bayley Scales of Infant and Toddler Development, 2nd edition (BSID-II)	1.28±0.04
13	Manji (2014)31	Tanzania	Randomised placebo-controlled trial	Birth cohort	206	Bayley Scales of Infant and Toddler Development, 3rd edition (BSID-III)	1.28±0.04
14	Sudfeld (2015)32	Tanzania	Randomised placebo-controlled trial	Birth cohort	958	Bayley Scales of Infant and Toddler Development, 3rd edition (BSID-III)	2.25±0.52
15	Locks (2016)33	Tanzania	Randomised placebo-controlled trial	Birth cohort	248	Bayley Scales of Infant and Toddler Development, 3rd edition (BSID-III)	1.21±0.03
Latin America
16	Santos (2011)34	Brazil	Longitudinal birth cohort survey	2004 Pelotas birth cohort	3868	Battelle Screening Developmental Inventory (BSDI)	1.99±0.05
17	Santos (2008)35	Brazil	Longitudinal birth cohort survey	Longitudinal, community-based cohort	365	Wechsler Pre-School and Primary Scale of Intelligence-Revised (WPPSI-R)	5.80±3.02
18	Fernald (2011)36	Ecuador	Randomised effectiveness trial	Prospective, community-based cohort	1265	MacArthur-Bates Communicative Development Inventory, short form, Spanish version	4.59±0.87
19	Handal (2008)37	Ecuador	Cross-sectional	Community based, selected using door-to-door survey	283	Ages and Stages Questionnaire (ASQ)	2.46±1.46
20	Braun (2012)38	Mexico	Prospective cohort study	Prospective, facility-based cohort	1032	Bayley Scales of Infant and Toddler Development, 2nd edition (BSID-II) McCarthy Scales of Children’s Abilities (MSCA)	2.02±0.03
Europe
21	Akman (2004)39	Europe-Turkey	Randomised clinical trial	Facility-based hospital	108	Bayley Scales of Infant and Toddler Development, 1st edition (BSID-I)	1.42±0.59