Question

why is foetus not considered as a parasite eventhough it contains foreign genetic material(i.e fathers genes)

Answer 1

Some of the arguments that favour that foetus is not a parasite are:

It develops from the fertilized cell within the body, while a parasite normally comes from outside

Parasite is usually harmful to the body , while foetus is not.

Parasite normally remains attached to the host by suckers etc but the foetus holds on to uterine lining only for a short duration, then becomes isolated in its amniotic sac.