2.4. Sample Size
The primary outcome of the ABC trial was defined as a CM-IgE level of 0.35 UA/mL or greater at 24 months of age. For sample size calculation, it was assumed that this outcome would be achieved in 10% of one group and 25% of the other, with a bilateral type I error of 5%, 90% power, and an estimated 3% loss to follow-up. Therefore, we calculated that a sample size of 300 participants in a 1:1 ratio would be required to detect this difference.