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Men with known low sperm count may be helped by cold sponging of the genitals. Daily cold sponging or showering should ideally continue for 3 months prior to trying for a boy as 70 days is the duration of spermatogenesis. This would give the sperm a boost from their very beginning. It would also be a test of heroism for the man! But, if it causes pain or discomfort, stop it.
Having said all that I have recently read a few articles suggesting that boys are more likely to be conceived following a period of hot weather.