→ The sex of the baby has been decided after completion of fertilisation.
→ The chromosome pattern in the human female is XX and in the male is XY.
→ Therefore, all the haploid gametes (ova) produced by the female have the sex chromosome X whereas in the male gametes (sperms) the sex chromosome could be either X or Y, hence, 50 per cent of sperms carry the X chromosome while the other 50 per cent carry the Y.
→ After fusion of the male and female gametes the zygote would carry either XX or XY depending on whether the sperm carrying X or Y fertilised the ovum.
→ The zygote carrying XX would develop into a female baby and XY would form a male.
→ That is why, scientifically it is correct to say that the sex of the baby is determined by the father and not by the mother.