Figure 4. Absolute risk reduction of delivery before 34 weeks and before 32 weeks.

PTD = preterm delivery. *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.