A series of three article and one commentary on maternal and child undernutrition reinforce the need to prevent undernutrition during the 1000 days from conception to age 2 years, with interventions both within and outside the health sector. Countdown researchers and their co-authors also issued a specific call for action on the unfinished undernutrition agenda. Published in The Lancet, these papers build upon findings from the previous 2008 and 2013 series, which established an evidence-based global agenda for tackling undernutrition over the past decade. The 2021 series:

• Describes how the evidence base for nutrition, health, food systems, social protection, and water, sanitation and hygiene interventions have evolved in the past 8 years, and
• Identifies the priority actions needed to regain and accelerate progress within the next decade.

The launch event took place on March 8, 2021, and a full recording can be accessed here. The series contributes to the Nutrition for Growth (N4G) Year of Action in 2021, which will culminate in the UN Food Systems Summit in September 2021 and the Tokyo N4G Summit in December 2021.

The three articles the Countdown investigators contributed to are:

Revisiting maternal and child undernutrition in low-income and middle-income countries: variable progress towards an unfinished agenda, by Cesar G Victora, Parul Christian, Luis Paulo Vidaletti, Giovanna Gatica-Dominguez, Purnima Menon, and Robert E Black.

Key messages from Victora and co-authors:

• From 2000 to 2015, there were small improvements in linear growth for children younger than 5 years, but progress was slow for wasting and low birthweight.
• The whole distributions of height-for-age and weight-for-height remain shifted towards undernutrition in low-income countries, where stunting and wasting persist as important public health problems.
• New evidence shows that the incidence of stunting and wasting are highest during the first 6 months of life, reinforcing the need to focus on the first 1000 days from conception to age 2 years.
• Socioeconomic inequalities persist as a major distal determinant of undernutrition, as shown by between-country and within-country analyses.
• Regarding micronutrient deficiency in young children, vitamin A status has improved in east Asia, but persists at high rates in south Asia and in Africa. Zinc deficiency affects one in every two children in the few countries with information. Anamia remains highly prevalent among women and young children. Investments to reduce undernutrition in women are important not only for women’s own health but also for the health and nutrition of their children, as new evidence reinforces the link between nutrition of mothers and reproductive outcomes.
• There have been positive yet small reductions in the prevalence of low body-mass index among women of reproductive age.
• The growing availability of anthropometric data for women and young children has allowed progress to be monitored and interventions to become more focused, but the scarcity of information on micronutrient status needs to be addressed.

Effective interventions to address maternal and child malnutrition: an update of the evidence, by Emily C Keats, Jai K Das, Rehana A Salam, Zohra S Lassi, Aamer Imdad, Robert E Black, and Zulfiqar A Bhutta.

Key messages from Keats and co-authors:

• Evidence-based interventions for improving maternal and child nutrition continue to be a combination of interventions that are direct (eg, delayed cord clamping and micronutrient supplementation, breastfeeding promotion, and counselling) and indirect (eg, malaria prevention, and water, sanitation, and hygiene promotion).
• Nutritional interventions delivered within and outside the health-care sector are equally crucial for preventing and managing malnutrition.
• New evidence supports the use of preventive lipid-based nutrient supplementation for reducing childhood stunting, wasting, and underweight, and the use of antenatal multiple micronutrient supplementation for preventing adverse pregnancy and birth outcomes.
• Evidence gaps remain for strategies to address malnutrition among schoolchildren and adolescents.
• The drivers of undernutrition are diverse, and novel evidence synthesis methods underscore the need for multisectoral action and coordination.

Mobilising evidence, data, and resources to achieve global maternal and child undernutrition targets and the Sustainable Development Goals: an agenda for action, by Rebecca A Heidkamp, Ellen Piwoz, Stuart Gillespie, Emily C Keats, Mary R D’Alimonte, Purnima Menon, Jai K Das, Augustin Flory, Jack W Clift, Marie T Ruel, Stephen Vosti, Jonathan Kweku Akuoku,  and Zulfiqar A Bhutta.

Key messages from Heidkamp and co-authors:

• The evidence base for direct and indirect health, agriculture and food systems, social protection, and water, sanitation, and hygiene (WASH) interventions to reduce undernutrition has grown substantially since the 2013 Lancet Series on maternal and child nutrition. However, information about the costs and cost-effectiveness of interventions delivered across sectors has not kept pace and remains a barrier to effective planning by governments.
• The available evidence reaffirms key priorities for undernutrition, including an emphasis on the first 1000 days (early pregnancy up until the first 2 years of child life). Interventions and actions targeting this age window require renewed commitment, new insights from implementation research, and fast-tracked funding to increase coverage and improve quality of service delivery.

• Several direct nutrition interventions are ready for scaling up in health systems and others appear promising; these policies should be considered for inclusion in national plans. Greater specificity about what direct and indirect actions health, agriculture and food systems, education, WASH, social protection, and other sectors should prioritise, in different contexts, is needed.

• A new body of evidence from in-depth analyses of successful stunting reduction at the national or subnational level reaffirms the need for a range of sectoral actions, especially those that address the underlying determinants of undernutrition, and the need to foster enabling environments.

Nutrition data and accountability have improved since 2013, but more action is needed to ensure that global goals and commitments can be tracked and, more importantly, that national and subnational actions across sectors are tailored to each specific context and reach the most vulnerable groups.

• A 2017 global Investment Framework for Nutrition estimated that, on average, an additional US$7 billion per year is required to reach global maternal and child undernutrition targets—a cost that will increase.