To determine whether gross motor scores of toddlers after complex cardiac surgery were different from fine motor scores and were adequately represented by motor composite scores and, whether acute care predictors and chronic childhood health markers of gross motor scores differed from those of fine motor.

This prospective inception-cohort outcomes study included 171 toddlers after complex cardiac surgery with cardiopulmonary bypass at age <6 months, born in Northern Alberta from 2009 to 2019, and without known chromosomal abnormalities. At a mean (standard deviation) age of 21.7 (3.7) months, the Bayley Scales of Infant and Toddler Development-III determined motor composite and scaled scores (normative values, 100 (15), 10 (3), respectively). The same variables from surgery and assessment were analysed using multivariate regression to predict gross and fine motor scores; results expressed as effect size (95% confidence interval) with % variance.

Composite, fine, and gross motor scores were 89.7 (14.2), 9.4 (2.5), and 7.2 (2.7), respectively. Predictive variables accounted for 21.2% of the variance for fine motor, and 36.9% for gross motor. Multivariate analysis for gross motor scores included toddlers need for cardiac medication, effect size (95% confidence interval) −0.801 (−1.62, −0.02), gastrostomy, −1.35 (−2.39, −0.319), and single ventricle, −0.93 (−1.71, −0.15). These same variables did not predict fine motor scores.

Gross motor skills commonly were lower than fine motor skills for toddlers after complex cardiac surgery. Predictors for gross motor scores differed from fine motor scores. Separate reporting of gross motor scores could lead to improved identification of predictors of delay and to optimised early intervention.