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Table 1 Statistical power for a trial sample size of 2300 with 1:1 randomization to vitamin D3 and placebo arms, and a nominal Type I error rate (alpha) of 0.05

From: Effect of maternal vitamin D3 supplementation on maternal health, birth outcomes, and infant growth among HIV-infected Tanzanian pregnant women: study protocol for a randomized controlled trial

Hazard ratio (HR) for maternal HIV progression (any increase in WHO HIV stage) or death
 Cumulative incidence over average 17 months follow-upa HR = 0.60 HR = 0.65 HR = 0.70
  12.5% 95.7% 88.3% 75.5%
  15% 98.0% 93.0% 82.3%
  17.5% 99.1% 95.8% 87.3%
Relative risk (RR) of small-for gestational age (SGA) birth
 Cumulative incidence of SGA in placebo arm RR = 0.65 RR = 0.70 RR = 0.75
  10% 98.4% 93.4% 81.2%
  12% 99.5% 96.9% 88.3%
  14% 99.9% 98.7% 93.0%
Relative risk (RR) of child stunting at 12 months of age (LAZ < –2)
 Cumulative incidence of stunting in placebo arm RR = 0.60 RR = 0.70 RR = 0.80
  15% >99.9% 98.8% 78.4%
  20% >99.9% >99.9% 90.3%
  25% >99.9% >99.9% 96.3%
  1. aAssumes the monthly incidence of maternal human immunodeficiency virus (HIV) progression or death is constant during follow-up
  2. LAZ length-for-age z-score, WHO World Health Organization