Developmental Milestone Attainment in US Children Before and During the COVID-19 Pandemic.

Importance: Restrictions related to the COVID-19 pandemic disrupted the lives of young children, but the association between the pandemic and any changes in early childhood developmental milestone achievement in the US remains unclear.

Objectives: To determine the association between the COVID-19 pandemic and changes in developmental screening scores among US children aged 0 to 5 years and to investigate whether caregivers self-reported more worries about their children or concerns about children's behavior during the pandemic, regardless of milestone achievement.

Design, Setting, And Participants: This was a cohort study using an interrupted time series analysis comparing prepandemic (March 1, 2018, to February 29, 2020), interruption (March 1 to May 31, 2020), and intrapandemic (June 1, 2020, to May 30, 2022) periods among 50 205 children (randomly sampled from a population of 502 052 children) aged 0 to 5 years whose parents or caregivers completed developmental screening at pediatric visits at US pediatric primary care practices participating in a web-based clinical process support system.

Exposure: COVID-19 pandemic period.

Main Outcomes And Measures: Age-standardized Ages and Stages Questionnaire, Third Edition (ASQ) domain scores (communication, personal-social, problem-solving, gross motor, fine motor), and rate of caregivers' concerns about the child's behavior or worries about the child as measured on the ASQ.

Results: A total of 50 205 children (25 852 [51.5%] male; mean [SD] age, 18.6 [16.0] months) and 134 342 ASQ observations were included. In adjusted models, significant age-specific mean score decreases from prepandemic to intrapandemic were observed in communication (-0.029; 95% CI, -0.041 to -0.017), problem-solving (-0.018; 95% CI, -0.030 to -0.006), and personal-social (-0.016; 95% CI, -0.028 to -0.004) domains. There were no changes in fine or gross motor domains prepandemic to intrapandemic. For infants aged 0 to 12 months, similar effect sizes were observed but only for communication (-0.027; 95% CI, -0.044 to -0.011) and problem-solving (-0.018; 95% CI, -0.035 to -0.001). After accounting for age-standardized ASQ scores, caregiver worries about the child increased slightly in the intrapandemic period compared with the prepandemic period (rate ratio, 1.088; 95% CI, 1.036-1.143), but there were no changes in caregiver concerns about the child's behavior. While changes in developmental screening scores were modest (2%-3%), nationwide, this could translate to more than 1500 additional recommended developmental referrals over baseline each month.

Conclusions And Relevance: Modest changes in developmental screening scores are reassuring in the short term but may tax an already overburdened developmental behavioral pediatrics infrastructure. Continued attention to developmental surveillance is critical since the long-term population- and individual-level implications of these changes are unclear.