3.1 Power calculation and F statistics
We calculated the power values and F statistics of included GWAS studies to evaluate whether our sample size was enough to explore the causal effect between BW and cancer risk. According to the previous articles and our meta-analysis reporting the odds ratio (OR) of each cancer52 and the interpretation of instrumental variables to BW, our study had an adequate statistical power (>80%) for statistical calculation. Our F statistics were range from 4802.59 to 81695.06 which meant that there was no evidence of weak instrument bias in our MR study. (Table 1)