IUI does NOT affect the sex ratio -- it does not make you more likely to have either a boy or a girl, using either fresh or frozen sperm. In the Shettles book Dr. Shettles claimed that most IUI births were boys, due to the fact that IUI is timed at ovulation -- this is NOT true.
There was a large-scale study comparing the outcome of IUI with fresh sperm vs. frozen sperm -- which compared birth outcome, sex, and other factors. Both groups had a 50/50 sex ratio.