Question

What is the scientific reason behind the birth of a boy or a girl

Answer 1

If the male lack of xy chromosomes then the the female will give birth to a girl as females already have xx chromosomes and if the male doesn't have lack of xy chromosomes then the female will give birth to a boy

Answer 2

If XX choromosome fertilise together then a girl child born and if XY choromosome fertilise together then a boy child born.