Materials and methods

We conducted a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines registered at the International Register of Systematic Prospective Reviews (PROSPERO) and approved under registration number CRD42019134431.

Results

Data synthesis

The search strategy resulted in 11,851 titles to examine. After removing duplicates (n=136 documents) and excluding 11,119 by title and abstracts, a list of 596 unique citations was assessed for eligibility. We identified 231 articles for full-text review (figure 1).

Note: Taken from PRISMA (2009)

Figure 1 Flowchart of studies selection 

The characteristics of the documents included in the review are presented in table 2. Most of the studies were conducted in multiple regions (n=84), followed by those in Africa (n=51) and Southeast Asia (n=44). The most frequent topics were stunting prevention (n=199), intersectoral collaboration (n=122), and nutritional interventions (n=71). Regarding the type of study, interventions were the most frequent (n=53), followed by cross-sectional (n=51), cohort (n=7), and cases and controls (n=2) studies. The sample size of the observational studies ranged from 48 to 699,686 participants. Data also included systematic reviews (n=10), qualitative studies (n=12), theoretical and conceptual documents (n=65), and health policies, infographics, and national guidelines (n=27).

Among life-course risk factors and interventions to prevent stunting, the most frequent was from 6 to 24 months (n = 196), followed by birth to 6 months (n=166), and pregnancy (n=141). We present here the results on stunting prevention, nutritional interventions, and intersectoral collaboration efforts evidenced in the literature. Table 3 shows study characteristics and life-course stages from pregnancy up to 24 months by region.

Table 3 Prevention of stunting in children under 2 years of age by life-course stage 

	N = 231		AFRO (1)		EMRO		EURO (3)		PAHO (4)		SEARO (5)		WPRO (6)		Multiple regions
	n	%	n	%	n	%	n	%	n	%	n	%	n	%	n	%
Pregnancy	141	61.0	24	17.0	4	2.8	0	0.0	15	10.6	33	23.4	7	5.0	58	41.1
Antenatal care	33	23.4	2	6.1	1	3.0	0	0.0	7	21.2	8	24.2	4	12.1	11	33.3
Education or counseling in nutrition for mothers and newborns	45	31.9	8	1 7.8	1	2.2	0	0.0	1	2.2	12	26.7	3	6.7	20	44.4
Mother's height	11	7.8	1	9.1	0	0.0	0	0.0	1	9.1	4	36.4	0	0.0	5	45.5
Micronutrient supplements	55	39.0	5	9.1	0	0.0	0	0.0	6	10.9	13	23.6	4	7.3	27	49.1
Adequate weight gain	15	10.6	4	26.7	0	0.0	0	0.0	0	0.0	3	20.0	1	6.7	7	46.7
Birth until 6 months of age	166	71.9	29	17.5	4	2.4	1	0.6	17	10.2	33	19.9	14	8.4	68	41.0
Low birth weight	19	11.4	3	15.8	0	0.0	0	0.0	3	15.8	3	15.8	2	10.5	8	42.1
Low height for age	6	3.6	0	0.0	0	0.0	0	0.0	1	16.7	2	33.3	1	16.7	2	33.3
Breastfeeding practices	71	42.8	9	12.7	3	4.2	0	0.0	6	8.5	16	22.5	3	4.2	34	47.9
Counseling in breastfeeding and nutrition	62	37.3	11	1 7.7	1	1.6	0	0.0	4	6.5	12	19.4	3	4.8	31	50.0
Micronutrient supplements	33	19.9	6	18.2	1	3.0	0	0.0	3	9.1	5	15.2	5	15.2	13	39.4
Early detection of infants at risk or with low HAZ	17	10.2	1	5.9	0	0.0	1	5.9	3	1 7.6	6	35.3	1	5.9	5	29.4
Growth and development control	33	19.9	4	12.1	0	0.0	1	3.0	6	18.2	8	24.2	2	6.1	12	36.4
Vaccines	21	12.7	3	14.3	2	9.5	0	0.0	1	4.8	4	19.0	2	9.5	9	42.9
6 to 24 months of age	196	84.8	37	18.9	6	3.1	2	1.0	22	11.2	36	18.4	13	6.6	80	40.8
Complementary feeding	100	51.0	16	16.0	2	2.0	1	1.0	6	6.0	19	19.0	7	7.0	49	49.0
Counseling in nutrition	83	42.3	15	18.1	1	1.2	1	1.2	5	6.0	12	14.5	7	8.4	42	50.6
Breastfeeding	52	26.5	8	15.4	1	1.9	0	0.0	5	9.6	12	23.1	3	5.8	23	44.2
Micronutrient supplements	72	36.7	13	18.1	2	2.8	0	0.0	8	11.1	15	20.8	5	6.9	29	40.3
Deworming	12	6.1	2	16.7	0	0.0	0	0.0	1	8.3	3	25.0	1	8.3	5	41.7
Early detection of infants at risk or with low HAZ	17	8.7	3	1 7.6	0	0.0	0	0.0	3	1 7.6	4	23.5	3	1 7.6	4	23.5
Growth and development control	41	20.9	8	19.5	0	0.0	1	2.4	7	1 7.1	8	19.5	4	9.8	13	31.7
Vaccines	23	11.7	3	13.0	1	4.3	0	0.0	1	4.3	3	13.0	4	1 7.4	11	47.8

HAZ: Height for age

Discussion

This systematic review of the literature is the first one to identify and describe stunting prevention strategies, associated factors, nutritional interventions, and intersectoral collaboration in children up to 2 years of age worldwide. It is useful for informing public health and policy decision-makers. Key findings indicated that:

There are knowledge gaps on intersectoral coordination for stunting prevention and/or intervention.

The strengths of this study are twofold: First, we complemented the collection and analysis of the most updated and high-quality data available with the revision of WHO, PAHO, and FAO official documents, as well as expert recommendations. Second, we characterized the evidence according to the life course from pregnancy to 2 years of age focused on prevention strategies, nutritional interventions, and intersectoral collaboration against stunting.

It has been suggested that stunting is an accurate indicator of inequalities in human development and that height-for-age is the best indicator of children's well-being ¹². The evidence found in this systematic review came mostly from the AFRO, SEARO, and PAHO regions where most interventions were conducted. Our findings show a region-specific description of actions to address stunting, where relevance and use depend on the country-specific context. Stunting tendencies from 1990 to 2012 showed that the number of stunted children under 5 was halved in Asia and the Latin America/Caribbean region, but its burden in Africa increased by 24% ¹. As various authors have argued, factors contributing to stunting correlate with poverty and socioeconomic development ^13-16. Black, et al., for example, concluded that in most countries, the prevalence of stunting among children under 5 was 2.5 times higher in the low-wealth quintile compared with the highest wealth quintile ⁸. Moreover, studies have demonstrated that a one-dollar increase in the per capita GDP was associated with a 0.003-unit decrease in stunting (p<.001) ¹⁷ and previous research using these platforms concluded that low stunting magnitudes were found in low- and middle-income countries with strong nutrition governance ¹⁷, which might be due to the existence of an intersectoral mechanism to address nutrition, the existence and adoption of a nutritional strategic plan, and national nutritional policies and/or dietary guidelines. These programs counted with resource allocation for the national nutrition plan, strategies, or policies, as well as the inclusion of nutrition monitoring and surveillance components in health budgets ¹⁷.

Critical sectors mentioned for stunting interventions were agriculture, health, education, social assistance programs, employment, and government ¹⁸. Several studies identified intersectoral coordination between health and other sectors. As an example of coordination between health and social sectors, conditional cash transfers were found to increase the use of health services and stunting surveillance ¹⁹ while social assistance programs allowed nutritional complementation for vulnerable homes with food insecurity ²⁰ and were considered helpful to reduce some of the limitations of families to invest optimally in their children. Such programs improved parents' knowledge about ideal practices to promote parenting and, also, had large impacts on parental behaviors and children's development in various contexts.

In some cases, social assistance programs including nutrition-specific objectives aligned with local needs and health services to increase access to food and nutritional supplements ²¹. Health literacy and nutrition knowledge were documented as activities where different sectors could participate and government actions geared towards the promotion of breastfeeding ²⁰. Researchers also evidenced coordination between community workers from the health and agriculture sectors to improve nutrition messages ²².

As for the evidence on stunting prevention by life-course, stage, and region, studies have shown that actions are required to strengthen the design and implementation of nutritional interventions. Stunting often begins in utero, according to India's National Family Health Survey 2005-2006 ¹². Antenatal control constitutes one of the most important factors to reduce stunting risk, as a pregnant woman who has at least one antenatal control has a 4.11% reduction in stunting odds ²³. Antenatal control is also a critical action to control adequate weight gain during pregnancy; its inadequacy is a strong predictor of low birth weight and other conditions related to malnourishment ²³.

The importance of adequate weight gain to prevent stunting was documented in pregnant women in Mozambique in the framework of research coordinated by the Ministries of Health and Women and Social Action. These recommendations are supported by scientific evidence and, furthermore, they are inexpensive and easy to implement at the primary healthcare level in any country. Micronutrient supplementation for pregnant women (i.e., iron and folic acid) has been found to prevent micronutrient deficiencies and contribute to linear growth improvement in many studies ^20,24-26.

A prevalent topic was adequate breastfeeding practices, particularly exclusive breastfeeding, during the first 6 months of life. Global strategies, such as Scaling Up Nutrition, 1000 Days, the Zero Hunger Challenge, and the Nutrition for Growth Summit, have demonstrated that early introduction of breastfeeding in the first hour after birth is a determinant factor for stunting prevention ^27,28. Individual or group-based counseling sessions to promote exclusive breastfeeding were reported as important interventions to scale up ²⁹. Other studies described the importance of the protection, promotion, and support of optimal breastfeeding practices, such as the initiation of breastfeeding within 1 hour of birth, exclusive breastfeeding counseling, lay support for breastfeeding through community-based and facility-based contacts, and additional control of the marketing of breastfeeding substitutes ³⁰.

Other important interventions, such as the surveillance of low birth weight and low birth height/length, were important for the early detection of infants at risk, as were low height for age, vaccination status, and close growth monitoring ⁹. Maternal health literacy and education ^31,32, as well as family nutrition practices based on the WHO infant and young child feeding guidelines ³³, prevented stunting.

Researchers have acknowledged the difficulties associated with the diagnosis of stunting despite the global consensus on how to define and measure it ¹². In some communities, short stature is the norm and linear growth is not routinely assessed in primary healthcare settings ¹². In this context, surveillance of stunted infants is critical because they are seemingly healthy. For this reason, the literature supports raising awareness and informing caregivers that short stature is a nutrition-related problem and linear growth is associated with adequate care ³⁴.

Interventions to address stunting are multifaceted ³⁰; they include breastfeeding education and counseling, appropriate complementary feeding, micronutrient supplementation of pregnant women, nutrition counseling during pregnancy, vitamin A supplementation in infants and children 6 to 59 months of age, and zinc supplementation in the management of diarrhea, which improves nutrient uptake ³⁵. These interventions often intertwine and stunting prevention messages take precedent over the specific catch-up growth messages ¹³.

The evidence synthesis in this systematic review clearly showed that a determinant factor in catch-up growth after a period of stunting was complementary feeding. Appropriate food introduction complementary to breastfeeding was relevant for catch-up growth with indicators such as minimum dietary diversity, minimum meal frequency, and minimum acceptable diet ^26,36,37. Intensive counseling and emphasis on dietary diversity together with the promotion and consumption of animal source foods are successful interventions to improve complementary feeding ^10,38.

Community workers and community participation were key to identifying pregnant women suffering from or at risk of food insecurity and helped to ease their route to health and social services; consequently, they facilitated the identification of adequate interventions for stunted children ^39,40. It has also been suggested that time constraints, maternal depression, lack of family support, and breastfeeding while working should all be taken into account and monitored in the surveillance of stunting or the risk thereof ²⁸.

As for intersectoral collaboration, the evidence highlighted a call to action from different sectors, but more is needed to develop indicators for the monitoring and evaluation of these partnerships. Linear growth improvement was possible through the national coordination of child and maternal nutrition services ²⁷. Evidence also showed that coordination should be clearly defined specifying what should be coordinated, how, and by whom ⁴¹. Plans to evaluate intersectoral coordination should also be considered ⁴². In Peru, establishing political commitment, cooperation, and coordination was acknowledged as a social, economic, and health challenge crucial for reducing stunting ⁴³. Mozambique stands out as an exceptional example, as specific roles and indicators were assigned to the health, social assistance, and educational sectors ⁴⁴. The goal was to qualify advisors in healthy feeding and nutrition from each of these sectors and monitor the partnerships with indicators at national, provincial, and district levels ⁴⁴. The literature also highlighted the importance of community mobilization and motivation to undertake initiatives for stunting prevention at the household level and to use services that improve child growth and development ³.

Sectors other than health have responsibilities in prevention and nutritional interventions against stunting. The education sector can develop strategies to reduce adolescent pregnancy and promote higher education and women's empowerment, for example ^15,45,46.

The economic development sector can aid the health sector by promoting community workers for stinting surveillance ²⁷; the communication sector is important for surveillance and intersectoral collaboration ²⁷; studies also supported the notion that the academic sector should share the responsibility of integrating the knowledge on breastfeeding and complementary feeding and their promotion ⁴¹. The private sector can contribute its experience in communications and financial support to develop plans aimed at reducing stunting at the national, provincial, and district levels ^42,44 as shown by the evidence on its relevance for food fortification in alignment with government policies ^27,42,47. Successful intersectoral collaboration strategies for the prevention of stunting and nutritional interventions to address it suggest that multiple sectors can target this public health problem by raising public awareness.

Thus, the recommendations from this review are applicable at multiple levels. Governments should strengthen national information and surveillance systems to produce data to support policy-makers response to nutrition priorities in a timely fashion. Indicators on stunting risks and their prevention, nutritional interventions, and intersectoral collaboration should all be included in the surveillance systems. Policymakers should raise awareness and train health workers on the importance of antenatal control and counseling regarding adequate weight gain during pregnancy. Lastly, more research is needed on epidemiologic surveillance indicators for the monitoring of prevention and catchup growth in infants from an intersectoral collaboration perspective.

Stunting is a worldwide concern and one of the Sustainable Development Goals to be accomplished in the short term. Worldwide evidence about prevention strategies, nutritional interventions, and intersectoral collaboration to address stunting and its risk factors highlights the need to strengthen vigilance and public health interventions. Linear growth is the best indicator of overall child development during the first years of life and human development inequalities. Efforts to assess the available information are necessary to create epidemiologic surveillance indicators, which provide guidance and individualized support to adopt public policies addressed to this problem and encourage the involvement of multiple sectors. All countries should promote the implementation of stunting surveillance and the construction of structured and standardized indices for international comparability and monitoring.

There were some limitations in the study. The comprehensive search terms used could reduce some relevant studies as gray literature. The gray literature may have contained additional information that was not included, and, finally, we gathered the information from multiple and heterogeneous sources, which represents a limitation for data standardization in specific variables due to different measurement methods.