There are two schools of thought on exercising while pregnant.

The first says, why bother? We spend our entire lives feeling guilty that we're not at the gym enough, that our arms aren't scuplted enough, that our bums are too big, that we ate that extra slice of dessert, that we had a croissant for breakfast instead of oatmeal. Pregnancy is the one time when we have a good excuse to indulge a little, lie on the couch instead of hit the gym.

This is the approach I took with my first pregnancy. Mind you, I walked the dog for an hour every day, and my pregnant stomach shrunk to the size of a walnut, so one extra bite would result in hours of heartburn... I could indulge in chocolate shakes only up to a point. I felt healthy enough.

It wasn't until after my son was born that I realized my abdominal muscles were completely gone (well, they are no matter how much you exercise), my hips had been stretched like rubber bands, my back had lost all strength, and my legs were too weak to properly lift the car seat without jacking up my back. When my 3 month old son was wearing 9 month old clothes, I ended up in physical therapy.

See, the other school of thought says that pregnancy is a time when you are training your body for the equivalent of a marathon. I know, the epidural makes it all numb and distant, but giving birth is a hugely physical act -- and the after-effects will stay with you for a long while.

This time around, I vowed to do it differently.

My acupuncture doctor advised no vigorous exercise during the first trimester. I eagerly complied, since I was so sick just getting off the couch required herculean effort. At week 14, she pronounced that I should begin some exercise to strengthen the pelvic floor. A couple of days later, I sneezed and peed. Oh no, I thought, this shouldn't happen until after the baby's born! I signed up for prenatal yoga that week.

In my first class, the teacher instructed us mamas in various stages of pregnancy into the plank position. And had us hold it, hugging our babies in. I could hardly breathe and my arms were shaking so badly I had to drop to my knees. But one mama, who was due that very week, held her plank position strong and smiling. I was impressed.

"There is no reason you cannot end your pregnancy stronger and with more endurance than when you started," our yoga teacher said.

So I'm working on that plank position. Yoga does it for me, but I've been doing yoga for over ten years, I know it's not for everyone. What worked for you?