How sex is determined in an unborn infant?

The sex of an individual is determined by the chromosomes present in his body. A normal human being consists of 23 pairs of chromosomes. Among this 22 pairs are autosomes responsible for the expression of body characters and one pair of chromosome is sex chromosome which determines the sex of an individual person. Males consist of XY chromosome and females consist of XX chromosome as sex chromosomes. During gamete formation only one of the either chromosomes in male or female enters into each gamete. So the gametes (sperm and egg) consist of one set of chromosome (haploid). The X-chromosome which fuses with Y-chromosome only produce a male child. So the sex of the unborn infant is determined by the type of sex chromosome of the male parent present in the zygote.