ISSUES Although maternal substance use is a known risk factor for child maltreatment, evidence on the scale of substance use is needed to inform prevention responses. This systematic review synthesised prevalence estimates of maternal substance use during pregnancy and early life among children at risk of maltreatment. Ovid, Pubmed, CINAHL, PsychInfo and ProQuest databases were searched. We included observational studies that sampled children at risk of maltreatment in high-income countries and reported information on maternal substance use during pregnancy and/or the child's first year of life. We extracted study characteristics and data to calculate prevalence, assessed risk of bias and conducted a narrative synthesis; there were insufficient comparable populations or outcomes to quantitatively synthesise results.

KEY FINDINGS Thirty five of 14,084 titles were included. Fifteen studies had adequately sized and representative samples to estimate prevalence. Maternal substance use prevalence ranged from 2.4% to 40.6%. Maternal substance use was highest among infants referred to child protection at birth (40.6%) and children in out-of-home care (10.4% to 37.2%). Prevalence was higher when studies defined substance use more broadly and when maternal substance use was ascertained from both child and mother records.

IMPLICATIONS Supportive, coordinated responses to maternal substance use are needed from health and child protection services, spanning alcohol and other drug treatment, antenatal and postnatal care.

CONCLUSIONS Prenatal and early life maternal substance use is common among child maltreatment populations, particularly among younger children and those with more serious maltreatment.