Why is there is a 50 percent chance a new born baby will be female?

There is sex chromosome in both male and female. Female has got XX chromosome. Man has got XY chromosome in the nucleus. So when you get an ovum, all of them have got X chromosome in them. When sperm form, you get half the sperms with X chromosome and half the chromosome have Y chromosome in them. So there are fifty percent sperms that are mean to be males and fifty percent chromosomes that are meant to be females. Which sperm will enter the ovum can not be known. So there are fifty fifty percent chances of baby becoming male or female.