Figure 4: RRs and 95% CIs of the risk of PTB comparing the PA intervention group to the control group among 9 interventional studies.

The pooled estimates (diamond data markers) were obtained using a random-effects model. The dots indicate the RRs for the risk of PTB comparing the intervention group to the control group. The size of the shaded square is proportional to the percentage weight of each study. The horizontal lines represent 95% CIs. CI: confidence interval; RR: relative risk.