

Of the 11,920 articles identified, we included 111 articles representing 102 unique RCTs. We used random-effects meta-regression models to assess potential effect modification by country-income level, child age, intervention content, duration, delivery, setting, and study quality. We calculated intervention effect sizes as the standardized mean difference (SMD) and estimated pooled effect sizes for each outcome separately using robust variance estimation meta-analytic approaches.

Parenting outcomes included parenting knowledge, parenting practices, parent–child interactions, and parental depressive symptoms. ECD outcomes included cognitive, language, motor, and socioemotional development, behavior problems, and attachment.

At least 2 reviewers independently screened, extracted data, and assessed study quality from eligible studies. We included randomized controlled trials (RCTs) of parenting interventions delivered during the first 3 years of life that evaluated at least 1 ECD outcome. We searched MEDLINE, Embase, PsycINFO, CINAHL, Web of Science, and Global Health Library for peer-reviewed, published articles from database inception until November 15, 2020.
