Risk factors for LBW include maternal anemia. A meta-analysis that included 11 experimental trials identified a significant 20% reduction in the risk of LBW associated with antenatal iron supplementation.<sup>24</sup> Risk factors for preterm births include zinc deficiency, parity and maternal age.

# **_4.2 Postnatal risk factors_**

During infancy and childhood, epidemiological studies point to suboptimal complementary feeding, recurrent infections and micronutrient deficiencies as important proximal determinants of stunting. Findings from the Cebu longitudinal study, for example, show that the likelihood of stunting is increased by diarrhea, febrile respiratory infections and early supplemental feeding.<sup>25</sup> Notably, the study finds a clear risk of early weaning off of breastmilk, identifying protective effects of breastfeeding and negative effects of supplementary feeding that were strongest in the first year of life, suggesting that among breast-fed infants _“high quality nutrients from breast milk are replaced with lower quality nutrients from weaning diets based on corn or rice”_ .

The existing experimental evidence suggests that nutrient supplementation, counseling for maternal, infant and young child feeding and the promotion of complementary feeding have been marginally successful at boosting linear growth (none have been able to normalize early childhood growth) and reducing the incidence of stunting. Experimental studies on breastfeeding promotion that included nutritional status outcomes did not show any effect on the length of infants (though the beneficial impact of breastfeeding in reducing mortality risk underpins why it is strongly promoted).<sup>26</sup> In response to the underwhelming effect of nutrient supplementation and counseling interventions on linear growth, three recent randomized controlled trials in Kenya, Bangladesh and Zimbabwe tested whether reduced exposure to pathogens in the environment are a key constraint to early growth among children. More specifically, these studies tested the hypothesis that environmental enteric dysfunction – a condition of the gut caused by fecal contamination which impairs nutrient absorption- is a key bottleneck for childhood growth, thus constraining the impact of nutrition interventions in settings with poor environmental conditions. In each of the studies, respondents were randomly assigned to receive water, sanitation, hygiene and nutrition interventions in isolation and in combination, testing whether synergies across different interventions exist.<sup>27</sup> In the Kenya study, none of the interventions reduced the incidence of diarrhea and only the nutrition intervention improved the growth of children.<sup>28</sup> In the Bangladesh study, all interventions reduced the incidence of diarrhea and again, only the nutrition intervention improved the growth of children, correcting one-sixth of the growth deficit compared to international norms of healthy growth. These studies were all consistent in their failure to find any effect of WSH interventions in isolation or in combination on the linear growth of children.

While not well established, there is some empirical evidence that points to the role of animal-sourced foods (ASFs) in the promotion of early childhood growth. Randomized control studies in Jamaica, China and Ecuador, for example, supplemented children’s usual diets with high protein milk, minced pork and eggs and in all cases found that treated children had grown taller than the control. In the Ecuador study, stunting prevalence among randomly assigned children who were provided one egg per day over a 6-month period declined by 47 percent relative to the to the control group of children who followed their usual diet.<sup>29</sup> A cluster randomized evaluation of the Philippines’ conditional cash transfer program, Pantawid Pamilyang Pilipino Program (PPP),<sup>30</sup> found the program reduced severe stunting among children (ages of 6 and 36 months) in the treated group by 10 percentage points, relative to children in the control.<sup>31</sup> To try and understand the possible mechanisms contributing to the large reduction in severe stunting, the study also reports the effects of Pantawid on the use of health services for children and on parenting practices, finding large impacts on the utilization of growth monitoring check-ups, vaccination and treatment for illness as well as an 8.2 percentage point (pp) increase in egg consumption and a 6.9 pp increase in dairy consumption relative to children in the control group. While 21