Which of the two, sperm or ovum, decides the sex of the child ?
Sperm
A baby’s sex is determined at the time of conception. When the baby is conceived, a chromosome from the sperm cell, either X or Y, fuses with the X chromosome in the egg cell, determining whether the baby will be female (XX) or male (XY). To be female, one needs to be (XX), whereas to be a male, (XY) is needed.