You would think the last thing anyone would want to do while it was bitter cold would be to get in the swimming pool. Yet, that's what I did this morning, and it felt good.

It was part of my new year's resolution to gain weight at a rate closer to what's recommended during pregnancy. You're supposed to gain about a pound a week (unless you're underweight or overweight), but I've been gaining 1.5 to 3 pounds. The holidays have not been kind!

While for the first few checkups, my ob-gyn just made a note of the weight gain, the last time, she recommended I try to get it under control. I knew she was right: if I continue at this rate, I'll gain back all the weight I'd lost nearly a decade ago, and then some.

So I enrolled in a water aerobics class at the local YMCA, after checking with my ob-gyn to make sure it was OK. I ordered a maternity bathing suit from FitMaternity.com, a retailer of maternity fitness clothes recommended by the Baby Bargains book. After doing a little comparison shopping, I discovered that their suits were the best price for maternity swimsuits, unless you just wanted something cute to wear when you're sunbathing.

I didn't expect the suit to arrive so soon, since I'd ordered it Friday. For my first class, I figured I'd have to jam myself into my two-piece tankini. While it still works (well, just barely), I was certain that my belly would pop out as soon as I raised my arms. Much to my delight, the maternity swimsuit arrived yesterday and fit perfectly.

The last time I took a water aerobics class was with my mom about 10 years ago, when I was living in my hometown. We signed up because we thought it would be easier on her arthritic joints than any other aerobic activity. She took to it right away: a cheerful smile on her face as we figured things out together. As always, she made easy friends with our classmates. In fact, she liked it so much, we re-enrolled after the first six-week course was over. But sadly, Mom declined to join me for another class, saying that even the heated pool wasn't warm enough for her joints.

Today, I showed up early to talk to the instructor ahead of time and find out if there should be any modifications to my movements. She wasn't there yet, so I sat on a bench. One of my fellow classmates, who introduced herself as Joanne, suggested I get in the pool with the other women. She'd point the instructor out when she arrived.

A few women were in the pool already, so I chatted with Joanne and a young woman named Michelle, who said she'd been in the pool for an hour or so, doing laps. She was on the larger side but seemed serious about getting into better shape. Another woman in her 30s told me that she'd taken the class while she was pregnant, up until the date that she delivered.

The class consisted of a range of ages and sizes: from women in their 30s, like me, to senior citizens; from relatively slim to obese. Water aerobics can be a great alternative for people with any number of physical difficulties, because it provides an almost no-impact workout. The buoyancy of the water can make it possible to do things that some of my classmates could probably never do in a regular aerobics class.

While we were waiting for the instructor, the other students began walking back and forth across the pool, chatting easily. I spoke to a woman about my age who was also taking her first class. When she found out I was pregnant (she didn't see me until I was half underwater, or it would have been obvious), she told me her son will soon be celebrating his eighth birthday.

The instructor was easy to spot: wearing a colorful Speedo swimsuit, the kind that serious swimmers wear, and carrying a little CD player. I made my way to the pool side to introduce myself.

When I'd called to register last week, the person who took the call had spoken to her about my joining, and she was the one who had said that I should be fine but should check with a doctor first. So after reassuring her that my doctor had given the go-ahead, I asked her if I should plan on any modifications to the activities. She recommended staying in the deeper water, since it would take the impact off any jumping or bouncing movements.

Like my classmate, she told me that she'd also done water aerobics while pregnant, up until her due date.

We began by walking back and forth across the pool. Everybody carried foam pool barbells, with which we could add resistance as we did different moves: such as pushing and pulling our arms ahead of us in the water. We also touched our elbow to our opposite knee and did a series of other actions.

This reminded me of what I used to do with one of my oldest friends (currently a single mother and lawyer in the Seattle area) in the community pool in the summertime. We would come up with strange ways to do laps across the pool, such as hopping on one foot or swimming by moving only one arm. Each time we finished a lap, we'd take turns deciding on the next strange movement. The difficulty of the movements, of course, was often compounded by the fact that we would laugh, sometimes uncontrollably, at each new challenge. Thoughts of that brought a smile to my face during the laps.

When we'd finished our laps, we placed our barbells on the side of the pool, and the women spread out for the aerobics portion of the class. Standing in the back, I found it a little hard to follow for several reasons.

First of all, there was a deep-water class going on behind me, of about three very large women wearing float belts that helped stabilize them in the deep water. As I understand it, that class is geared towards people who would have difficulty with a regular water aerobics class. While I couldn't hear what they were saying, the constant noise of voices was distracting.

Secondly, I had trouble seeing what movements our instructor was doing under the water. I seem to remember that our instructor for the class Mom and I took handled things differently. She would demonstrate movements before having us start them, and she added new movements much more slowly. This instructor changed movements about every eight beats, without any set routine.

It might have been easier if I'd been standing next to someone who really knew what she was doing. However, I was next to someone who was either equally lost or who, for reasons of her own, was restricting herself primarily to arm movements.

Still, I've taken enough aerobics classes in my day (for about 20 years, give or take), that I knew the most important part is just to do my best and keep moving. Since we took our pulse three different times during the class, I know that I was, indeed, getting a workout.

Already, as I dictated this while walking the dog, I could feel the effects of the exercise in the back of my leg. Now, at home typing, I can feel it in my arms and shoulders. The best part, though, is that I could actually do all the movements without difficulty, and I never felt as if I was straining.

Even though part of me wishes Mom could be with me, enjoying this class, I think it's going to be a great addition to my routine as I seek a fit pregnancy.