basically the 'male' sperm are faster but smaller and weaker so do not survive as long as the 'female' sperm. So if you have sex further away from ovulation there is more liklyhood of the male sperm having died before ovulation occuring. But if you have sex say the day before ovulation, they are the faster swimmers so more likly to get there first. Acidity is a very important factor too. The female womb is very acidic to sperm and kills it. Some women have very acidic wombs so find it very hard to concieve boys. If you orgasam at the time of coneption this also helps the liklyhood of having a boy, as this caused the womb to become more alkaline briefly. There are a number of things you can do to influence the sex of your child, including your OH having either a hot or cold bath before sex as this also affects the numbers of each spem type and some dietary changes. You can get books on this that claim to be 95% accurate at helping you determ the sex of your child.
