Background
Undernutrition in early childhood is associated with a range of negative outcomes across the lifespan. Little is known about the prevalence of exposure to undernutrition among young children with significant cognitive delay.

Method
Secondary analysis of data collected on 161 188 three‐ and four‐year‐old children in 47 low‐income and middle‐income countries in Rounds 4–6 of UNICEF's Multiple Indicator Cluster Surveys. Of these, 12.3% (95% confidence interval 11.8–12.8%) showed evidence of significant cognitive delay.

Results
In both middle‐income and low‐income countries, significant cognitive delay was associated with an increased prevalence of exposure to three indicators of undernutrition (underweight, wasting and stunting). Overall, children with significant cognitive delay were more than twice as likely than their peers to be exposed to severe underweight, severe wasting and severe stunting. Among children with significant cognitive delay (and after controlling for country economic classification group), relative household wealth was the strongest and most consistent predictor of exposure to undernutrition.

Conclusions
Given that undernutrition in early childhood is associated with a range of negative outcomes in later life, it is possible that undernutrition in early childhood may play an important role in accounting for health inequalities and inequities experienced by people with significant cognitive delay in low‐income and middle‐income countries.