Blackrose - I agree that it is mostly luck too.

It doesn't matter what proportion sperm is produced in it is what comes out that matters, pun intended.

There is some interesting articles which I have read which indicate that the tendency to produce one gender over another in families is inherited from the male, leading to the conclusion that there is a genetic tendency in some male to produce semen which contains more than one sex over another.

Other factors which have been found to alter the X versus Y chromosones in semen in males are:
- age
- climate
- occupation
to name just a few. The Y chromosome is shorter than the X and more fragile so it is thought to be more at risk of damage therefore even if sperm is produced in equal amounts, it doesn't necessary come out that way, and it can even vary from day to day, week to week. Heat is a common source of damage to sperm and also lifestyle factors can affect it too. Of course female factor can also influence things so it just turns out to be a bit of luck to see how things turn out.

All things being equal the natural ratio of baby boys born to baby girls is 105 to 100, giving a natural birthrate of 51.2% male and 48.8% female.

Back to the original question, regardless of any other factors you are always more likely to have a boy.

So if you have two boys first, then there is more of a chance that the third will also be a boy. Even if you have two girls first, you are more likely to have a boy third but of course there is a high chance of a girl too independently of there being any factors which make one gender more likely than another.

75% of families with three children actually contain 2 genders. Only 25% are single gender.

TICKLISH