Table 1 Characteristics of included studies (in chronological order)

Bailey 1983[48]

101 pregnant women aged 15–41 years

1. Standard WIC program- Monthly vouchers for specified quantities of milk, canned fish, carrots, cereal, cheese, eggs. 6 monthly nutrition education and health care referrals n=43

Controlled before and after study

Serum iron, vitamin B6, folic acid,

12 weeks

High

WIC clinic and hospital prenatal clinic, Florida, USA

WIC and control participants recruited from different prenatal clinics at 30 weeks gestation

Red cell folate

2. Routine antenatal care through hospital clinic n=58

Follow-up period 12 weeks

Dietary iron, vitamin B6, and folic acid

Birth weight

% Low birth weight

Metcoff 1985[42]

824 pregnant women stratified by predicted birth weight; all WIC eligible

1.Standard WIC program with research assessments and routine prenatal care n=238

Randomised controlled trial

Birth weight

~21 weeks

High

Plasma B-carotene

Hospital prenatal clinic, Oklahoma City, Oklahoma, USA

Maternal weight

All participants recruited from same hospital prenatal clinic

2. Routine prenatal care with research assessments n=172

Follow-up period 24 weeks

Plasma amino acids

3. Routine prenatal care n=353

Caan 1987[38]

703 post-partum women- all WIC participants prenatally

1. Standard WIC program maintained for 6 months post-partum for non-lactating women n=333

Controlled before and after study

Birth weight

6 months

High

Low birth weight

Macrosomia

48 local WIC agencies, California, USA

All WIC participants prenatally, divided into control &intervention groups retrospectively based on WIC benefits post-partum

2. Standard WIC entitlement for 0–2 months post-partum n=309

Maternal Hb

Follow-up period-duration of prenatal care in second pregnancy

Maternal BMI

Rush 1988a[44]

11,154,673 pregnant women from 1392 US counties in 19 states

1. Standard WIC program

Interrupted time series

Birth weight

Duration of prenatal WIC participation

Low

Duration of gestation

National sample of counties, USA

WIC participants increased over time from 0 to 39% from government reports

Follow-up period 1972-1981

Fetal mortality (>28 weeks)

Infant mortality rate

Inadequate prenatal care

Rush 1988b&c[45, 47]

6563 pregnant women, all WIC eligible by income

1. Standard WIC program and research assessments n=5205

Controlled before and after study

Nutrient intake

Duration of prenatal WIC participation

High

174 WIC clinics and 55 prenatal clinics, national sample, USA

WIC participants recruited at WIC clinics, controls recruited at public prenatal clinics in counties with low WIC coverage

2. Routine antenatal care and research assessments n=1358

Follow-up period 6–9 months

Mean nutrient intake % RDA

Anthropometry

Duration of gestation

Birth weight

Fetal mortality

Rush 1988c&d[45, 46]

5004 pregnant women, mean age 22.4 years

1. Standard WIC program n=4219

Controlled before and after study

Family food expenditure

Duration of prenatal WIC participation

High

174 WIC clinics and 55 prenatal clinics, national sample, USA

2. Routine antenatal care n=785

Family grocery expenditure

WIC participants recruited at WIC clinics, controls recruited at public prenatal clinics in counties with low WIC coverage

A subset of women were asked to complete a food diary at follow-up: WIC n=1031, Control n=551

Follow-up period 6–9 months

Family meals out expenditure

Gunnell 2000[39]

1089 children aged 2–14 years, mean age 8 years

1. Daily school feeding soup/milk, halibut oil capsules, oranges or milk and marmite n=298

Controlled before and after study

Height

12 months

Moderate

Leg length

8 rural and urban locations in Scotland and England, UK

Disadvantaged families selected and divided into intervention and control groups arbitrarily

2. Family food packages weekly-milk, cheese, wheat germ, marmite, oranges, cod liver oil, eggs n=269

Follow-up period 13 months for children′s growth and 60 years for mortality

Mortality

School in adjacent areas were also selected as intervention and controls non-randomly

3. No food subsidy- control families n=261

4. No food subsidy- control schools n=258

Pehrsson 2001[43]

110 post-partum non-lactating females >18 years old, all WIC participants prenatally

1. Standard WIC program for 6 months post-partum n=57

Controlled before and after study

Haemoglobin

6 months

Low

Transferrin receptor

Urban WIC clinics, Maryland, USA

Participants recruited at WIC clinics in different counties

2. Standard WIC program for 0–2 months post-partum n=53

Follow-up period 6 months

Anaemia %

Ferritin

Burr 2007[37]

190 pregnant females aged >=17 yo

1. Vouchers for free 2L fruit juice weekly (home delivery) n=63

Randomised controlled trial

Frequency of specific fruit consumption

Throughout prenatal care period (~30 weeks)

High

District hospital prenatal clinic, Wales, UK (disadvantaged area)

All participants recruited from one hospital prenatal clinic at booking visit

2. Advice/written information from midwives to promote fruit intake during pregnancy n=63

Follow-up period 30 weeks

Serum β-carotene

3. Routine antenatal care n=64

Herman 2006 & 2008[32, 40]

602 post-partum women >18yo- all WIC participants

1. $10 voucher weekly for F&V at local supermarket plus standard WIC program n=200

Controlled before and after study

F&V intake

6 months

High

3 WIC clinics, Los Angeles, California, USA

Intervention and control participants recruited at three separate WIC clinics with similar socio-demographics

2. $10 voucher weekly for F&V at local farmers market plus standard WIC program n=200

Follow-up period 1 year

3. Standard WIC program n=202

Currie 2008[49]

All pregnant Californian women 1961–1974 n=4864673

1. Standard Food Stamp Program- monthly food vouchers for any foods up to $200/person/month dependent on income and household size

Interrupted time series

Median birthweight

Duration of prenatal FSP participation

Low

Low birthweight rate

California, USA

Food stamp participation rates by county used to calculate impacts

Follow-up period 1961-1974

Probability of birthweight <specified cut-off

Hoynes 2009[18]

28,000,000 pregnant women in the 2059 US counties with a WIC program by 1979 (85% of US births in the 1970s)

1. Standard WIC program

Interrupted time series

Birth weight

Duration of prenatal WIC enrolment

Low

National sample of counties, USA

Follow-up period

% Low birth weight

WIC participation estimated from government reports

1971-75 & 1978-82

Kennedy 2009[41]

40 African-American women aged >18yrs, non-pregnant

1. F&V $10/week with recipes from mobile store at community centre, monthly nutrition education, cooking demonstrations and anthropometric assessment n=20

Randomised controlled trial

Fruit and vegetable consumption

6 months

High

Community centre, East Baton Rouge, Louisiana, USA

Participants recruited by local community advertising and personal communication

2. Monthly anthropometric assessment and written nutrition education n=20

Follow-up period 6 months

Weight

BMI

BP

Quality of life

General and emotional health

Ni Mhurchu 2010[30]

1104 adult >18 years, main household shopper, 86% female

1. Tailored nutrition education– computer-generated messages and shopping lists plus generic recipes monthly by mail n=274

Randomised controlled trial

Total food purchased

6 months

Low

8 supermarkets in Wellington, Wanganui and New Plymouth, NZ

Follow-up period

Healthy food purchased

Participants recruited by mail invitation, supermarket advertisements and community group promotion (for Maori and Pacific communities)

2. Price discount of 12.5% on healthy foods applied automatically at check-out n=275

15 months

Less healthy food purchased

F&V purchased

3. Price discount plus tailored nutrition education n=277

Macronutrients purchased

4. Control n=278