well it depends on both parents X chromosomes from the Father and Y from the mother fight it out in an ultimate Battle of death for the Sexes!
Actually that is NOT **the case. The X chromosome is always from the mother. The father either contributes another X (XX = a girl) or a Y (XY = a boy). There is no "Mom's X & Dad's Y battling it out" going on. The dad has both an X & a Y. And if there is any battling going on; it's between the **DAD's X and the DAD's Y.
*The determination of the gender is COMPLETELY up to the father. *
And unless people are willing to take some really unromantic steps, there is not way for **EITHER **party to predetermine the gender of the child.