Abstract: We included 34 studies, which includes one that was a follow-up study and 20 that were rated as being at high risk of bias. We conducted 14 meta-analyses assessing physical outcomes post-intervention. Nine meta-analyses showed significant findings favouring the intervention group for weight (MD -965.25 g; 95% CI -1360.52 to -569.98), length (MD -1.30 cm; 95% CI -1.60 to -1.00), head circumference (MD -0.81 cm; 95% CI -1.18 to -0.45), arm circumference (MD -0.47 cm; 95% CI -0.80 to -0.13), leg circumference (MD -0.31 cm; 95% CI -0.49 to -0.13), 24-hour sleep duration (MD -0.91 hr; 95% CI -1.51 to -0.30), time spent crying/fussing (MD -0.36; 95% CI -0.52 to -0.19), deceased levels of blood bilirubin (MD -38.11 mmol/L; 95% CI -50.61 to -25.61), and there were fewer cases of diarrhoea, RR 0.39; 95% CI 0.20 to 0.76). Non-significant results were obtained for cortisol levels, mean increase in duration of night sleep, mean increase in 24-hour sleep and for number of cases of upper respiratory tract disease and anaemia. Sensitivity analyses were conducted for weight, length and head circumference, and only the finding for length remained significant following removal of studies judged to be at high risk of bias. These three outcomes were the only ones that could also be meta-analysed at follow-up; although both weight and head circumference continued to be significant at 6-month follow-up, these findings were obtained from studies conducted in Eastern countries only. No sensitivity analyses were possible. We conducted 18 meta-analyses measuring aspects of mental health and development. A significant effect favouring the intervention group was found for gross motor skills (SMD -0.44; 95% CI -0.70 to -0.18), fine motor skills (SMD -0.61; 95% CI -0.87 to -0.35), personal and social behaviour (SMD -0.90; 95% CI -1.61 to -0.18) and psychomotor development (SMD -0.35; 95% CI -0.54 to -0.15); although the first three findings were obtained from only two studies, one of which was rated as being at high risk of bias, and the finding for psychomotor development was not maintained following following removal of studies judged to be at high risk of bias in a sensitivity analysis. No significant differences were found for a range of aspects of infant temperament, parent-infant interaction and mental development. Only parent-infant interaction could be meta-analysed at follow-up, and the result was again not significant. These findings do not currently support the use of infant massage with low-risk groups of parents and infants. Available evidence is of poor quality, and many studies do not address the biological plausibility of the outcomes being measured, or the mechanisms by which change might be achieved. Future research should focus on the impact of infant massage in higher-risk groups (for example, demographically and socially deprived parent-infant dyads), where there may be more potential for change.

Plain-language summary: This review aimed to assess the impact of infant massage on mental and physical outcomes for healthy mother-infant dyads in the first six months of life. A total of 34 randomised trials were included. Twenty of these had significant problems with their design and the way they were carried out. This means that the we are not as confident as we would otherwise be that the findings are valid. That is to say, the findings of these 20 included studies may over- or under-estimate the true effect of massage therapy. We combined the data for 14 outcomes measured physical health and 18 outcomes measured aspects of mental health or development. The results show limited statistically significant benefits for a number of aspects of physical health (for example, weight, length, head/arm/leg circumference, 24-hour sleep duration; time spent crying or fussing; blood bilirubin and number of episodes of illness) and mental health/development (for example, fine/gross motor skills personal and social behaviour and psychomotor development). However, all significant results were lost either at later follow-up points or when we removed the large number of studies regarded to be at high risk of bias. These findings do not currently support the use of infant massage with low-risk population groups of parents and infants. The results obtained from this review may be due to the poor quality of many of the included studies, the failure to address the mechanisms by which infant massage could have an impact on the outcomes being assessed, and the inclusion of inappropriate outcomes for population groups (such as weight gain). Future research should focus on the benefits of infant massage for higher-risk population groups (for example, socially deprived parent-infant dyads), the duration of massage programmes, and could address differences between babies being massaged by parents or healthcare professionals.