My wife and I have always joked (although it's true) that we know EXACTLY when and where we got pregnant and we weren't really trying. The first time was in a hotel in Cocoa Beach, Florida and the second time was during a hotel stay in New Hampshire. And, yes, we DID have sex outside of any vacation or hotel stay.
I loved sex with my wife when she was pregnant, especially for the first few months. It seemed that she was hornier than usual and made for great sex. Once her breasts started to swell and her belly began to show, we changed positions but had a great time. In fact, we had sex the day before our second son was born.
Now, the down-time post birth wasn't great.