Appendix Figure. Illustration of calculation in Table 2, using the outcome of delivery before 34 weeks in the more selective high-risk group.

BV = bacterial vaginosis; PTD = preterm delivery. *To calculate the confidence limits for the increase or decrease in adverse outcome, plug in the confidence limits of effect size here. A negative sign (–) indicates a net increase in adverse outcomes (harm), and a positive sign (+) indicates a net decrease in adverse outcomes (benefit).