Background:
Tobacco smoking and smoke exposure during pregnancy and childhood cause considerable childhood morbidity and mortality. We aimed to determine whether implementation of the World Health Organization's recommended tobacco control policies (MPOWER) were of benefit to perinatal and child health.

Methods:
We searched 19 electronic databases, hand-searched references and citations, and consulted experts to identify (quasi-)experimental studies assessing the association between implementation of MPOWER policies and child health. Our primary outcomes of interest were: perinatal mortality, preterm birth, hospital attendance for asthma exacerbations, and hospital attendance for respiratory tract infections (RTIs). Where possible and appropriate, we combined data from different studies in random-effects meta-analyses.

Results:
We identified 41 eligible studies that assessed (combinations of) MPOWER policies: smoke-free legislation (n=35), tobacco taxation (n=11), and smoking cessation services (n=3). Following implementation of smoke-free legislation, rates of preterm birth decreased by -3.77% (10 studies, 27,530,183 individuals; 95%CI -6.37 to -1.16), hospital attendance for asthma exacerbations decreased by -9.83% (five studies, 684,826 events; 95%CI -16.62 to -3.04), and hospital attendance for RTIs decreased by -3.45% (two studies, 1,681,020 events; 95%CI -4.64, -2.25) for all RTIs, and by -18.48% (three studies, 887,414 events; 95%CI -32.79 to -4.17) for lower RTIs. Associations appeared to be stronger when comprehensive smoke-free laws were implemented. Among two studies assessing the association between smoke-free legislation and perinatal mortality, one demonstrated significant reductions in stillbirth and neonatal mortality. Meta-analysis of studies on other MPOWER policies was not possible; all four studies on increasing tobacco taxation and one of two on offering disadvantaged pregnant women help to quit smoking that reported on our primary outcomes had positive findings.

Conclusions:
Smoke-free legislation is associated with substantial child health benefits. The majority of studies on other MPOWER policies also indicated positive impact. These findings provide strong support to implement such policies comprehensively across the globe.