Table 2

Participant characteristics in included studies of early childhood development interventions delivered by healthcare providers

Study author, year	Country	No of infants*	Description of caregiver/infant	Sex of child (male (%))	Primary caregiver	Age of mother
Ara et al, 2019123	Bangladesh LMIC	378	Married pregnant women aged 16–49 years	Not recorded	All mothers	Mean age in years (SD) intervention: 23.38 (4.0), control: 23.54 (4.32)
Aracena et al, 2009122	Chile HIC	90	Primiparous adolescent mothers living in an extremely poor neighbourhood	Intervention 61%, control 45%	All mothers	Mean age in years (SD) intervention: 17.3 (0.23), control: 17.15 (0.22)
Armstrong et al, 1999121	Australia HIC	181	High-risk mothers with at least one liveborn infant	Not recorded	All mothers	Mean age in years (SD) intervention: 25.72 (5.61), control: 26.67 (6.08)
Barlow et al, 2003117	England HIC	131	Vulnerable/high-risk women	Intervention 52%, control 48%	All mothers	<17 years n (%) intervention: 12 (17.9), control: 14 (22.2)
Barnes et al, 2013116	England HIC	166	Expectant mothers with low educational qualifications and/or less than 20 years of age	Intervention 54%, control 63%	All mothers	Mean age in years (SD) intervention: 21.7 (1.9), control: 21.9 (1.6)
Black et al, 1994113	USA HIC	60	Low-income, inner-city, multiparous, polydrug misusers	Intervention 45%, control 59%	All mothers	Mean age in years (SE) intervention: 26.4 (0.9), control: 27.9 (0.7)
Brooten et al, 1986112	USA HIC	79	Infants with birth weights of 1500 g or less	Not recorded	All mothers	Mean age in years (SD) intervention: 24 (7), control: 23 (6)
Butz et al, 2001111	USA HIC	117	Mothers who used cocaine and/or opiates	Intervention 41%, control 59%	Mother 69%, other 31%	Mean age in years at infant birth (SD) intervention: 28.9 (4.5), control: 28.0 (4.6)
Cooper et al, 2009104	South Africa LMIC	449	Women in the last trimester of their pregnancy	Intervention 48%, control 48%	All mothers	Mean age in years (SD) intervention: 25.5 (5.23), control: 26.2 (5.84)
Cooper et al, 2015105	England HIC	301	Primiparous women at risk of postnatal depression	Intervention 38%, control 46%	All mothers	Mean age in years (SD) intervention: 27.94 (5.4), control: 28.66 (6.0)
Cremer et al, 1977101	Colombia LMIC	148	Mothers in the first/second trimester of pregnancy with at least 50% of their other children classified as malnourished	Not recorded	Not recorded	Not recorded
El-Mohandes et al, 2003100	USA HIC	286	Mothers receiving no or inadequate prenatal care	Not recorded	All mothers	Mean age in years intervention: 24.8, control: 25.2
Fatori et al, 201999	Brazil LMIC	80	Low-income pregnant youth aged 14–19 years	Not recorded	All mothers	Mean age in years (SD) intervention: 16.9 (1.3), control: 17.3 (1.2)
Gardner et al, 200396	Jamaica LMIC	140	Low-income women with infants with birth weight <2500 g	Intervention 41%, control 46%	All mothers	Mean age in years (SD) intervention: 23.0 (6.6), control: 24.6 (7.3)
Goldfeld et al, 201795	Australia HIC	722	Pregnant mothers <37 weeks’ gestation with 2 or more of 10 risk factors	Intervention 46%, control 44%	All mothers	Mean age in years (SD) intervention: 27.5 (6.1), control: 27.8 (6.4)
Gray et al, 197992	USA HIC	100	Women who had their first or second child at the Colorado General Hospital	Not recorded	Not recorded	Not recorded
Guteilus et al, 197791	USA HIC	95	Primiparous mothers who were black, unmarried and between 15 and 18 years of age	Not recorded	Mothers or grandmothers	Not recorded
Infante-Rivard et al, 198990	Canada HIC	47	Mothers from low socioeconomic background	Not recorded	All mothers	Mean age in years (SD) intervention: 25.3 (5.7), control: 23.5 (3.8)
Jack et al, 201589	Canada HIC	739	Primiparous pregnant women (<24 years) with <28 weeks’ gestation experiencing socioeconomic disadvantage	Not recorded	All mothers	Mean age in years for total sample (SD) 19.76 (2.36)
Jungmann et al, 201088	Germany HIC	755	Primiparous low-income mothers between their 12th and 28th week of pregnancy	Not recorded	All mothers	Mean age in years (SD) intervention: 21.27 (4.2), control: 21.53 (4.4)
Kemp et al, 200884	Australia HIC	208	At-risk mothers from a disadvantaged community	Not recorded	All mothers	Mean age in years (SD) intervention: 27.6 (6.7), control: 27.7 (5.9)
Kitzman et al, 199781	USA HIC	1139	Primiparous women less than 29 weeks pregnant with sociodemographic risks	Not recorded	All mothers	Mean age in years (SD) intervention: 18.1 (3.2), control: 18.1 (3.3)
Korfmacher et al, 1999—RCT 179	USA HIC	490	Primiparous women	Not recorded	All mothers	Mean age in years (SD) intervention: 20.24 (4.17), control: 19.70 (4.13)
Korfmacher et al, 1999—RCT 279	USA HIC	500	Primiparous women	Not recorded	All mothers	Mean age in years (SD) intervention: 19.44 (3.69), control: 19.70 (4.13)
Letourneau, 2001a76	Canada HIC	24	Primiparous inexperienced adolescent mothers aged between 13 and 19 years	Not recorded	All mothers	Mean age in years at time of infant birth (SD) for total sample 18.06 (1.01)
Mejdoubi et al, 201174	The Netherlands HIC	460	High-risk primiparous women	Not recorded	All mothers	Mean age in years (SD) intervention: 19.5 (2.8), control: 19.2 (2.6)
Minkovitz et al, 200170	USA HIC	2235	Not recorded	Not recorded	All mothers	<20 years (%) intervention: 15.2, control: 14.9 20–29 years (%) intervention: 53.0, control: 51.5 ≥30 years (%) intervention: 31.8, control: 33.5
Norr et al, 200367	USA HIC	477	Low-income, inner-city women in neighbourhoods with high infant mortality	Not recorded	All mothers	Under the age of 20 (%) intervention: 105 (40.7), control 85 (38.8)
Olds et al, 198662	USA HIC	400	Primiparous women	Not recorded	All mothers	Mean age in years intervention: 19.53, control: 19.57
Owen-Jones et al, 201356	England HIC	1645	Nulliparous pregnant women aged 19 years or under	Not recorded	All mothers	Mean age in years (range) intervention: 17.9 (17.0–18.8), control: 17.9 (16.9–18.8)
Resnick et al, 198855	USA HIC	41	Premature infants weighing <1800 g at birth	Intervention 52%, control 40%	Not recorded	Mean age in years (SD) intervention: 24.0 (5.8), control: 24.9 (7.8)
Rotheram-Borus et al, 201450	South Africa LMIC	1190	Pregnant women at least 18 years old	Not recorded	All mothers	Mean age in years (SD) intervention: 26.5 (5.5), control: 26.3 (5.6)
Sadler et al, 201349	USA HIC	105	Primiparous women aged 14–25 years	Intervention 51%, control 52%	All mothers	Mean age in years (SD) intervention: 19.5 (2.6), control: 19.7 (2.8)
Salo et al, 201947	Finland HIC	45	Mothers with depressive symptoms	Not recorded	All mothers	Not recorded
Siegel et al, 1980—RCT 146	USA HIC	99	Low-income women in their third trimester	Not recorded	All mothers	Mean age in years intervention: 21.3, control: 19.8
Siegel et al, 1980—RCT 246	USA HIC	105	Low-income women in their third trimester	Not recorded	All mothers	Mean age in years intervention: 20.6, control: 19.8
Siegel et al, 1980—RCT 346	USA HIC	112	Low-income women in their third trimester	Not recorded	All mothers	Mean age in years intervention: 20.7, control: 21.0
Slade et al, 202044	USA HIC	164	Primiparous mothers aged between 14 and 25 years	Intervention 52%, control 53%	All mothers	Mean age in years (SD) intervention: 20.1 (2.8), control: 20.0 (2.5)
Tsiantis et al, 199640	Cyprus, Greece, Yugoslavia, Portugal HIC	Not recorded	Not recorded	Not recorded	All mothers	Not recorded
Wallander et al, 2010—RCT 137	India, Pakistan, Zambia LMIC	164	Infants with birth asphyxia who were unresponsive to bag and mask ventilation	Intervention 59%, control 61%	All mothers	Mean age in years (SD) intervention: 24.6 (5.5), control: 24.2 (4.0)
Wallander et al, 2010—RCT 237	India, Pakistan, Zambia LMIC	243	Infants without birth asphyxia who did not require any resuscitation	Intervention 54%, control 58%	All mothers	Mean age in years (SD) intervention: 25.5 (5.1), control: 25.6 (5.7)
Yousafzai et al, 201415	Pakistan LMIC	751	Mothers from a predominantly rural and impoverished community	Intervention 55%, control 55%	All mothers	Not recorded

*Number of infants randomised.
HIC, high-income country; LMIC, low/middle-income country; RCT, randomised controlled trial.