Figure 3. Study characteristics and absolute risk reduction of delivery before 37 weeks.

Span = treatment timing spans less than 20 weeks and greater than 20 weeks. *Baseline risk is the percentage of deliveries before 37 weeks in the placebo group. Absolute risk reduction is the difference in probability of delivery before 37 weeks (control minus treatment). McDonald et al. (58) and Carey et al. (57) performed a high-risk group subanalysis; high-risk group is included in total study population of the average-risk target group. Odendaal et al. (50) included 2 target populations; high-risk and low-risk groups are 2 separate groups.