Personally, I think that it's good to breathe fresh air in countryside. I always go hiking since I was 4 mths up till 9 mths. Of course, the hiking path should be very safety and not tough at all. Usually, I walked only 1 to 1.5 hours. You can take rest whenever you feel like.
Now, I'm in week 37 and I've already stopped doing exercises. My foot has started to swell this week. But I don't have any back pain problem.