140 is the magic number. Stuff can still be challenging - actually during pregnancy I'm find even simple stuff a little tougher! - you just gotta be flexible. Why don't you try swimming laps a few times a week? It's a different cardio to running (I used to knock out a quick 8km on my lunch break most days & trained all the way up to 1/2 mara before getting ill & having to take a long break) & you'll find it challenging at least at first, then it can become part of your weekly routine when you fall pregnant.
I would decrease your weights at first while your muscles learn & grow to compensate for your pregnancy joints. The key is to learn not to push so hard at first, & listen to your body. My mantra used to be Go into the pain - it helped me run 15km in just over an hour once (*nostalgic tear in eye*) but that's just not the way in pregnancy - you gotta think about blood flow to the baby (the faster your heart is beating, the less blood per beat which means less for you AND for baby), you gotta consider the risk of developmental issues if you, & by association your little one, get too hot. They're resilient in their little bat cave, but they're also sensitive!! HTH.
ETA:Oh & yep, this all starts early on. It's why we feel horribly tired during early pregnancy, to make us slow down!!