Last night my girlfriend told me she's pregnant. Should I start having sex with her now?

Tie them to a nearby pole for the meantime. I would recommend steel cables if you can get your hands on some, but rope will do in a pinch as long as it's not windy or raining. If there's too much slack, add a couple of dowel rods. That'll also help stabilize everything, and I highly recommend them for a longer session.