Abstract:
BACKGROUND : Knowledge about typical development is of fundamental importance for understanding and promoting
child health and development. We aimed to ascertain when healthy children in four culturally and linguistically different
countries attain developmental milestones and to identify similarities and differences across sexes and countries.
METHODS : In this cross-sectional, observational study, we recruited children aged 0–42 months and their caregivers between
March 3, 2011, and May 18, 2015, at 22 health clinics in Argentina, India, South Africa, and Turkey. We obtained a healthy
subsample, which excluded children with a low birthweight, perinatal complications, chronic illness, undernutrition, or
anaemia, and children with missing health data. Using the Guide for Monitoring Child Development, caregivers described
their child’s development in seven domains: expressive and receptive language, gross and fine motor, play, relating, and
self-help. Clinicians examining the children also completed a checklist about the child’s health status. We used logit and
probit regression models based on the lowest deviance information criterion to generate Bayesian point estimates and
95% credible intervals for the 50th percentile ages of attainment of 106 milestones. We assessed the significance of
differences between sexes and countries using predefined criteria and regions of practical equivalence.
FINDINGS : Of 10 246 children recruited, 4949 children (48·3%) were included in the healthy subsample. For the
106 milestones assessed, the median age of attainment was equivalent for 102 (96%) milestones across sexes and
81 (76%) milestones across the four countries. Across countries, median ages of attainment were equivalent for all play
milestones, 20 (77%) of 26 expressive language milestones, ten (67%) of 15 receptive language milestones, nine (82%) of
11 fine motor milestones, 14 (88%) of 16 gross motor milestones, and eight (73%) of 11 relating milestones. However,
across the four countries the median age of attainment was equivalent for only two (22%) of nine milestones in the
self-help domain.
INTERPRETATION : The ages of attainment of developmental milestones in healthy children, and the similarities and
differences across sexes and country samples might aid the development of international tools to guide policy, service
delivery, and intervention research, particularly in low-income and middle-income countries.
