It's true, keeping up or starting a good fitness routine while pregnant is extremely beneficial. From improving mom's cardiovascular health and maintaining strength to improving blood flow to the placenta (aka nutrient center for baby). But exercising while pregnant can be confusing. Your OBGYN and pregnancy books may advise staying away from activities that can throw off your balance like bike riding or horse back riding and suggest doing gentle exercises like walking and swimming. And while walking and swimming are great choices for low impact cardio, it's important to incorporate strength training into your exercise routine. Strength training helps to maintain muscle and burn off excess calories better and for a longer period after exercise than cardio training alone. And while aiming to burn off calories for weight loss is never the goal for exercising while pregnant, it sure does help to keep your weight in check especially with all the cravings or midnight hunger strikes!
Improving core strength is essential to assist in stabilizing your shifting pelvis while it grows a human. Planks are one of my favorite exercises because it not only works the midsection, but also targets the shoulders and quads. However, it is important to modify as you progress in your pregnancy.
First Trimester: no modifications needed here if you were able to perform a traditional plank before pregnancy. As you get towards the end of your first you may want to switch to second trimester modifications.
Second Trimester: decrease the stress on your midsection by dropping down to your knees or performing them with arms elevated like on a chair or the end of the couch.
Third Trimester: By this point properly engaging your core can be tough so it's best to work your core in a different way. Either go up to a wall and perform a plank there, focusing on engaging the transverse abdominus or, my preferred method, is doing a reverse plank. You still need to focus on engaging the transverse but there is much less chance of coning in this position.