Twenty-one studies (3,823 participants) were included in the review; 15 were RCTs (one with historical controls). One study scored 6 on risk of bias, three scored 5, three scored 4, seven scored 3 and seven studies scored 1 or 2.
Compared to controls, women who received the interventions gained statistically significantly less weight (WMD -1.54kg, 95% CI -1.86 to -1.21; 19 studies, 22 study arms; evidence of statistical heterogeneity I²=86%). Separate analyses showed that dietary interventions were significantly more effective at limiting gestational weight gain compared to physical activity or mixed interventions (results reported in the review).
Six of the eight theory-based studies (75%) reported favourable results on gestational weight gain in the intervention group. Ten of 13 studies (77%) that were not theory-based reported positive intervention effects.
The most effective interventions included the behaviour change techniques of providing information on the consequences of behaviour to the individual, providing rewards contingent on successful behaviour, prompt self-monitoring of behaviour and motivational interviewing. None of these behaviour change techniques were present in dietary or physical activity interventions. Other findings were reported in the review.