Table 3 Intervention description by type, theory of change and target population

Almond et al [34]

Conditional cash transfer

Food Stamp Program is the most expansive of US Food and Nutrition Program. Benefits are an important part of the program and they vary in amount through time (ex. around 200$ per recipient household per month in 2011) and can be used to purchase all food items

The absence/presence of this program at county level was used to study its effect on birth weight

Eligible low income US residents

Baker et al [38]

Earned Income Tax Credit

The Earned Income Tax Credit (EITC) is the largest poverty alleviation program in the US, It involves a tax rebate to low-income families contingent upon their employment, with larger benefits for recipients with children. Individuals with no earned income are not eligible. The size of the credit increases with increasing earned income, eventually plateauing followed by a phase-out of benefits. Initiated in 1975, the program was expanded in 1993, creating substantial variation in the size of the tax credit awarded to recipients. Individual states also offered differing amounts of earned income tax credits that underwent expansions during the study period. The quasi-random nature of these variations – in that they are unassociated with individual characteristics – presents the opportunity to more clearly identify the impacts of the EITC on health

Low-income families in the United States contingent upon having an earned income

Brownell et al [23]

Unconditional Cash Transfer

Healthy Baby Prenatal Benefit is an unconditional cash transfer of max 81.41 Can$ per month given during the second and third trimesters of pregnancy. It was given monthly upon request if they fit eligibility criteria (documented annual incomes below Can$32,000 and pregnancy confirmed by a physician)

All women receiving welfare during pregnancy in Manitoba province- Canada

Chung et al [33]

Universal Unconditional Cash transfer

The benefit is a fund dividend, provided from Alaska’s government, to each Alaska’s resident. It is an unconditional cash transfer that was given for two years: 1982 and 1983. The amount was of $1,000 per person in nominal dollars in 1982 $386.15 per person in 1983

All residents in Alaska in 1982 and 1983

Leyland et al [22]

Conditional cash Transfer

The HiP grant was a universal conditional cash transfer of £190 for women reaching 25 weeks of pregnancy if they had sought health advice from a doctor or midwife. It was intended to provide additional financial support in the last months of pregnancy to contribute towards a healthy lifestyle. The grant was introduced for women with a due date on or after 6 April 2009 and subsequently withdrawn for women reaching the 25th week of pregnancy on or after 1 January 2011

All women in Scotland (but the intervention was delivered through all Great Britain and Northern Ireland from 2009 to 2011) reaching 25 weeks of pregnancy if they had sought health advice from a doctor or midwife

Hamad et al 2015 [29]

Earned Income Tax Credit

Same as described by Baker et al

Low-income families in the United States contingent upon having an earned income

Hamad et al 2016 [30]

Earned Income Tax Credit

Same as described by Baker et al

See above

Hoynes et al [31]

Earned Income Tax Credit

Same as described by Baker et al

Single mothers aged 18 and older with singleton births

Komro et al 2019 [26]

Earned Income Tax Credit

Same as described by Baker et al

Single mothers aged 18 and older with singleton births

Komro et al 2016 [36]

Minimum Wage Salary

The minimum wage for workers is the lowest remuneration that employers can legally pay their employees. In the United States it is regulated both at state-level and federal level. The laws underwent several changes in time and this study examined relative changes in law and amount by month from 1980 through 2011, calculating the difference between state-level minimum wage and the federal minimum wage in each state and month. All calculations have been adjusted for inflation by expressing all differences in 2011 dollars

All United States population- in particular it affects low educated individuals

Milligan et al [25]

Unconditional cash transfer

Starting in 1998, the core Canada Child Tax Benefit was augmented with a new program called the National Child Benefit. Under the National Child Benefit program, the federal government provided a cash benefit called the National Child Benefit Supplement (NCBS). By 2008, the NCBS reached monthly rates of Canadian $169 for a first child, $149 for a second, and $142 for subsequent children

In 2001, the province of Manitoba changed its approach to the NCBS. Prior to 2001, Manitoba was one of the provinces that reduced welfare checks when a family received the NCBS, dollar for dollar. However, starting in 2001, Manitoba ended this “clawback” for children age zero to five. Furthermore, in 2003, the clawback exemption was extended to all children age zero to eleven. This policy reform implied an increase in income for families. Also the receipt of the NCBS check was not conditional upon parents employment

Low-income families eligible for the NCBS checks. Authors focussed on all children aged 0 to 5 years between the years 1999 and 2005. Years from 2001 onward were coded as being “after” the policy change

Morris et al [24]

Conditional cash transfer

The Self-Sufficiency Project (SSP)was a demonstration program designed to make work a viable alternative to welfare for low-income parents, whose skills and experience would likely relegate them to low-paying jobs. SSP’s financial supplement paid parents who left welfare and worked at least 30 h per week half the difference between their actual earnings and a target level of earnings. The target earnings were set at Can$30,000 in New Brunswick and Can$37,000 in British Columbia a year

Single parents in British Columbia and New Brunswick who had been on welfare for at least a year were selected at random from the welfare rolls between November 1992 and March 1995

Rosenthal et al [35]

Conditional Cash Transfer

In November 1999, Las Vegas introduced a program to encourage members to seek prenatal care in the first trimester of pregnancy to complement its traditional high-risk maternity management program. The program offered US$100 to both the pregnant member and the member’s network obstetrician or midwife after delivery upon verification that the patient entered care during the first trimester and completed regular visits thereafter

Pregnant women enrolled in the program from 1998 to 2001

Strully et al [27]

Earned Income Tax Credit

Same as described by Baker et al

Low-income families in the United States contingent upon having an earned income

Wehby et al [37]

Minimum Wage Salary

The minimum wage for workers is the lowest remuneration that employers can legally pay their employees. In the United States it is regulated both at state-level and federal level. The laws underwent several changes in time and this study examined changes in amount by month from 1989 to 2012 Over the sample period (1988–2012), the federal minimum wage increased from $3.35 to $7.25 and they examined the real ($2012) minimum wage, which is the nominal wage deflated by the consumer price index

All United States population- in particular it affects low educated individuals

Wicks-Lim et al [32]

Earned Income Tax Credit

Same as described by Baker et al. but the study focus only on New York state expansion and examined the effects at neighbourhood level

Low income neighbourhood in Yew York City