Sample size
RECRUITMENT
Details of the original study sample size calculation were included in the previously published protocol. Briefly, we estimated that a sample of 40 women (20 in each arm) would allow us to estimate the overall recruitment rate per woman with SCD to within 10% of the true value or better using the Clopper-Pearson exact Binomial method for a 95% confidence interval. Assuming a 50–60% recruitment rate and an estimated 20% loss to follow-up, we planned to recruit 50 participants over an 18-month period in order to reach a final sample of 40 women.