Now that I'm entering into my third trimester, I'm starting to feel just how pregnant I really am—especially when it comes to working out. Obviously, my growing baby bump and extra weight make my usual workouts more challenging, but I pay close attention to how my body feels from day to day, which has helped me stay active throughout my pregnancy so far. (Though I have had to tweak my routine...more on that below.)

Nowadays, it's well established that women who were active before getting pregnant can safely remain active. But, of course, every woman's pregnancy is different and you should talk to your doctor about your current habits or before starting a new exercise routine. That said, here are 7 things you need to know about working out during pregnancy.

Your body may tell you to dial things back

Early on in my pregnancy, I noticed that my body was telling me to slow down. I'm an avid CrossFitter and runner, and I immediately noticed how labored my breathing became during cardio workouts. My running pace slowed drastically and I even needed to take breaks in the middle of workouts in order to catch my breath. But I knew I wasn't alone when it came to listening to my body and dialing back on my exercise efforts. In 2011, veteran marathoner Amber Miller ran the Chicago Marathon at 39 weeks pregnant (she had received permission from her doctor to run half the race and walk the other half) and finished in 6:25:50 when her usual time was around 3:30.

You might feel more tired during and after workouts

I felt a lot more tired during and after my workouts, especially during my first trimester. Initially, I was really surprised and even a bit frustrated, but I knew I needed to listen to my body. After all, it was working hard enough making another human! I didn't beat myself up over my new activity level, and I did what I could. Bonus: Being active actually helped ease some of my morning sickness (at least for a little while) so I still looked forward to my regular workouts.

You might need to switch up your workouts entirely

Prior to getting pregnant, I was training for a half-marathon, so I was running a decent amount of miles each week. But toward the end of my first trimester, running became a lot more difficult. I felt like I had no lungs and couldn't breathe, so I cut back on running. My weekly mileage has continued to decline since then, but I don't let it bother me. Instead, I focused my attention on other forms of exercise to keep me moving. Now, I attend regular CrossFit and cycling classes—which I do at my own pace and comfort level—and they agree more with my body and how I'm feeling.

You might feel weird in the locker room

When my bump really started growing, I felt a little awkward during my workouts. Thankfully, no one ever said anything snippy to me, but I did get a few weird looks here and there. My doctor knew all about my pre-pregnancy exercise regimen and she supported my decision to remain active. Her only exercise restriction: "Stop if something feels uncomfortable." She said my body would tell me what was too much way before I ever did any harm to my unborn baby. Even still, I know I'm in good company when it comes to fit mamas. Celebrity trainer Tracy Anderson, yoga instructor Hilaria Baldwin, and Health contributing fitness editor Kristin McGee all have prenatal workout DVDs.

You'll need to take a LOT more bathroom breaks

Without fail, I use the bathroom at least twice during an hour-long fitness class. Sometimes, I'll make 3 or even 4 trips! Staying hydrated is especially important during pregnancy, so I try not to let all of those frequent bathroom breaks bother me. I just sneak out of class whenever there's a lull between activities, so I don't miss too much when nature calls.

You'll need longer workout tops 

As my belly grows and grows, I’ve had the toughest time finding workout gear that actually fits and doesn’t look totally ridiculous on me. I've found that lightweight, extra long workout tops are the most comfortable. They move with me, so they don't ride up and expose my belly every time I lift my arms overhead.

You'll have ups and downs

I had awful morning sickness during my first trimester, so my workouts were less than stellar. But ever since I entered my second trimester, I feel so much better and almost like my pre-pregnancy self. My energy has returned, so I've been able to get into a groove with my workouts. I'm not sure what the third trimester will hold for me, but I hope I can stay as active as possible until the end of my pregnancy.

Read Tina’s daily food and fitness blog, Carrots ‘N’ Cake.