Isn’t an embryo/foetus a parasite? I understand that this could be a sensitive issue for some and I apologise if it actually offends anyone.
Not exactly as parasitism normally refers to an organism living with another organism where the parasite obtains benefits from a host which it usually injures.
From www.m-w.com
That depends on how you define “parasite.”
Note these definitions.
I would say that a fetus is not a parasite, since a parasite does not benefit the host, and genetic survival is, at least theoretically, a benefit.
I suspect this one is going to end up in either Great Debates or IMHO.
I strongly suspect that there is a pro-choice argument lurking at the heart of this question. To answer the OP: No. An embryo/foetus is not a parasite. The “purpose” of living things, in the sense that they have a purpose, is to reproduce and continue the species. The mammalian reproductive strategy of the young developing inside the mother evolved because it was advantageous to the species. Parasitism, as opposed to symbiosis, is not generally thought of as advantageous to the host species.
No.
Embryos are parasites only as much as birthed children are.
Both leech off their hosts, but as long as the host likes them or perceives some sort of benefit from them, it’s all fine and dandy. Or the host is just stupid. Me, I never understood why anyone would want to have kids 
I disagree Ponster, a fetus certainly does fit the definition of parasite in the link you provided. So what? It’s a semantic issue. Just because two things can fit in the same definition doesn’t mean they are the same thing.
What? Are you saying that even if something fits a definition, that definition doesn’t necessarily apply to it?
The definition of parasite that I learned specified that the two organisms must be of different species–so no, a fetus is not a parasite, in my world
Aha, I have long figured that they are parasites, but timidly feared to express that view.
I mean, “genetic survival” is a pretty hypothetical or indiirect “benefit”, surely.
That’s not what I said at all, in fact just the opposite. The fact that most people do not consider a baby to be a parasite doesn’t change the fact that it does fit most definitions. Sattua’s definition makes a lot more sense to me but the different species stipulation isn’t in my dictionary. Any logical flaw might be in thinking that definitions alawys are or should be mutually exclusive to each other.
I may have to write a science fiction story where a creature is a true biological parasite to othes of its own species.
What part of “parasite obtains benefits from a host ** which it usually injures.**” from the Merrion Webster dictionary applies to a foetus?
The same way any other parasite injures its host – it leeches off the host and drains its resources without providing any physical benefit in return.
In my copy of the Merriam Webster Collegiate Dictionary (10th edition), parasite refers to parasitisim, the definition of which is: an intimate association between organisms of two or more kinds; especially one in which a parasite obtains benefits from a host which it usually injures.
One could also read “organisms of two or more kinds” to be species per Sattua’s understanding.
So if you read the definition with the assumptions that a parasite must injure the host and be of another species, no, a fetus is NOT a parasite.
Frankly, the faster this thread gets out of GQ and into GD, the better.
Try “commensalism” – the inbetween stage between parasitism and mutualistic symbiosis. The commensal organism lives inside the host but does not injure it, other than perhaps diverting some nutrients from the host’s ingestion of foodstuffs.
To me it all depends on how you interpret the definitions. There was a time, within living memory, when the potential for survival in old age depended on having at least one child willing to provide for you when you became too enfeebled to completely care for yourself. Hence pregnancy could easily be seen as a time-binding mutualism: divert your resources to the embryo now, and it will grow into an adult which will provide care for you in the future.
Compare two 40 year old twins who have lead identical lives apart from one having no children and the other having given birth multiple times.
usually != always
It isn’t fiction.
Deep Sea Angler Fish
There are some differences. One is that the ‘host’s’ body is designed to hold, nurture and protect the ‘parisite’. Also the ‘parisite’s’ creation is from the genetic material of the mother (and father), and the begining of the parisite’s life is created inside the mother.
Also the whole issue that one of the main points of life is to reproduce itself, with or without the conscent of the ‘host’.
Somebody’s been watching the Alien Trilogy with his little brother again, hasn’t he? 
Interesting link, one thing about it:
It would seem like reporduction, though having simular aspects to a parasite/host relationship, is sort of a unique seperate relationship.
Perhaps just a nitpic, but I want to make sure I’s not missing anything, The mother’s placenta I would think is the placenta that she had when she was attached to her mother. The placenta is the baby’s placenta.
Anyway even here with the fish, it appears that there is a benefit to the host, that of reporduction.