Many pregnant women embrace the miracle of motherhood and their hormone-fueled, Häagen-Dazs-powered derrières. Others squeeze into the last pair of black leggings that still fit and hit the gym.

The American College of Obstetricians and Gynecologists urges pregnant women to exercise for 30 minutes daily; this includes the evenings when all you desire is to prop up your puffy feet and watch “Deal or No Deal.” And the list of positive effects of exercise is impressive: generally a “healthier” pregnancy, reduced risk for gestational diabetes, stronger muscle tone for labor, decreased levels of anxiety, and of course, the one they leave out — protecting yourself from turning into a goddess of cellulite. I’m seven months pregnant, and my obstetrician concurred and gave me the green light to “climb every mountain” with the following guidelines: Stay hydrated, avoid sports that rely heavily on balance and put me at risk of falling, monitor my heart rate — keeping it at fewer than 140 beats a minute — and use the workout talk test of “Can I chat while jogging?”

No problem. I’ll try not to gain too much weight, but to not gain too little; ingest 400 milligrams of fish oil a day, but limit tuna intake; heat my food, but stand far away from the microwave; soak in a warm bath, but not too warm; sleep on my left side, not my right side; eat yogurt; not clean the litter box, and wear compression stockings. And continue to exercise every day, but not let my heart rate go above 140. Sure.

In my first trimester, I cycled in mountainous Croatia, ran, and swam. The exercise restrictions felt like a secret — a contract among me, my baby, my doctor, and my husband. My obstetrician’s rules seemed easy to follow, until I woke up one morning spotting. What went wrong? Too much Warrior Flow Yoga? Did my heart rate monitor work?

And that’s when I heard them: the urban legends of exercising pregnant women who didn’t play by the rules. “My sister’s friend ran the NYC half marathon at six months.”

“My neighbor trekked to Mount Everest’s Base Camp at four months. She delivered early; her kid is a genius.” “I ran five miles a day with each of my four kids, including the days I gave birth to twins.”

A little more pregnant and a little more cautious, I worked with a personal trainer to tailor a prenatal exercise routine. But there were still nights that I wondered if I pushed myself too hard. I’d get sharp pain in my pelvis or tightness in my stomach. Am I in labor? Did my trainer have a clue? As it turns out, pregnancy — all on its own — has a great deal of aches and pains. My workouts were fine.

Now my belly is the size of a spacious, one-bedroom baby condo, and I’m still gym-bound. Climbing in and out of a cab is difficult, picking up my dog’s waste is murder, so hitting the elliptical machine is no longer a cakewalk. Onlookers at the gym flash that “you go, girl” look. My trainer helps me tie my shoes. My routine now consists of prenatal Hatha yoga, swimming, light weights, and lots of sighing.

Most recently, with my doctor’s blessing, I vacationed in Vail, Colo., where I did not ski but opted for a leisurely snowshoe. Granted, I’d put on my sun block, and my heart rate monitor would read 127 beats a minute.

To be among the snowcapped evergreen trees, even at my slowed pace, was exhilarating. Then I returned home to discover: “Exercise at altitudes over 7,500 feet has been identified as unsafe,” according to the Web site American-Pregnancy.org. Vail is at 8,000 feet! I felt horrible.

Alas, nothing is ever cut and dried with prenatal exercise — and everyone has an opinion. When my doorman notices me in gym clothes, he dispenses his own prenatal workout advice: “Walk a lot and drink loads of milk.” The homeless man on Eighth Avenue and 25th Street cries: “Looking good! Now don’t wear heels!” He’s got my back.

Ms. Koutas Poch is the author of “I (Heart) My In-Laws” (Owl).