And oh yeah - on the subject of using the mother's body to survive, actually a foetus uses the placenta to survive, which grows as a result of being pregnant. Sure - the placenta takes it's nutrients from the mother's body, but apart from the misaligned pelvis, extreme tiredness, back pain, carpal tunnel syndrome, sore and bleeding gums, varicose veins, haemarrhoids, weight gain, headaches, moodiness, awkwardness, inability to get up from a sitting or lying position without three or four tries, and a few other things, you hardly notice.
And the second trimester is the most fun I've ever had in my life. I've never felt so utterly amazing. Plus, not getting your period for almost a year is pretty much worth anything - without the added bonus of beautiful kicking baby at the end.....