You want this baby. At 40-something, your clock has about three minutes to go. It's a boy, a healthy, everything-looks-normal boy.

Seven years ago, you were indoctrinated into the world of boys. Who would have thought one of your deepest and most profound relationships would be with someone who guzzles glasses of chocolate milk and devours goldfish crackers by the handful?

Through the grainy gray blur of the ultrasound, you see this new boy's hand. All five fingers reaching out through the watery murk, as if to say, "Hello, what's for dinner?"

Ob gyn: "Sacrifices will have to be made."

You: "All right."

Ob-gyn: (in a serious tone) "When you exercise, the blood flow shifts to your muscles, lungs and heart, away from your internal organs, and that means your uterus. If you exercise too strenuously, you can restrict oxygen from your uterus."

You: (nodding)

Your husband: (a stern look on his face) "Are you listening to this?"

A confession: Your vice, of all things, is exercise -- intense, the sweatier-the-better, pain-inducing, move-till-you-drop exercise. One-hundred-mile bike races, marathons, 6 a.m. spin classes, weights, balls, kettle balls, steps, bands. Like crack to an addict or an exuberant salad bar to a vegetarian.

Ob gyn: "Walking is good. Swimming, too."

Caveat: This advice is not for everyone, just you, because of your history, your addiction/obsession/habit (see above), your age, your high-risk status with alarms blaring.

Your husband buys you white sneakers with cushy rubber soles, so cushy you feel like you're bouncing on small mattresses.

Just so you understand, you look up the definition of walking: "to roam, wander; to move about in visible form; to move along on foot, advance by steps."

At first you blast music, anything to distract from the plodding left-right-left-right-left-right, moving about in your visible form. My God! What idiot invented walking? Don't look at the stream-lined cyclists streaking by in tight Lycra and svelte runners showing off their calves, because you want that -- the wind rush, the heavy breathing, the heart-pounding endorphin fix, all of it. This line of thinking goes on for a while.

Eventually, you grow tired of drums and guitars and women wailing, so you turn to lectures. Why not walk and become smarter at the same time? You download seminars about Renaissance art, the history of religion, world literature, philosophy, the human brain. After enduring hours of drone, it's doubtful you're becoming smarter; it's certain you're gaining weight at a remarkable rate.

Fact #1: (read when motivation wanes) Exercise during pregnancy can help a baby's automatic nervous system -- the beating of the heart, blood pressure and breathing rate.

Fact #2: Pregnancy can sap you (so can carrying around a 15-pound bag of potatoes, which is what you feel like at 26 weeks), but regular exercise can give you a boost of energy.

Fact #3 (from a supportive friend who sees something noble in this undertaking): Henry David Thoreau spent four hours a day sauntering through the woods, hills and fields. He said to walk like a camel, which he thought was the only beast that ruminated when walking.

One day you forget to recharge your iPod, and now is the time to walk because you have to go to work and grocery shop and stop at the vet for dog medicine and go to the drugstore for prenatal vitamins and pick up your kid at school. So you put on your mattress shoes and head out -- in silence.

Holy cow! How will you last 40 minutes? Didn't you read somewhere that silence is a torture method, ranking up there with sleep deprivation? How will you endure this? You remember Fact #1. When it loses its punch, you turn to Fact #2. Five minutes have gone by. You develop new respect for Zen monks and prisoners in solitary confinement.

You're about to turn back when you hear something. Birds. Actual birds are singing songs.

Then it's as if the sound gates open and in rush dogs barking, lawn mowers and leaf blowers buzzing, sprinklers spraying and chipmunks chattering. Without the white noise of music or academics' droning, you begin to see: lime green leaves fluttering on the birch tree, the magnolia showing off cream-colored buds, like scoops of vanilla ice cream, and bees swarming the blue rosemary flowers.

At 28 weeks, you fit in two walks a day because the morning air -- crisp, fresh, alert, with the clouds sitting on the land -- is so different from the afternoon air, which is thicker with foliage and cloud or heat. You smell cut grass, the chlorine from a pool, the scent of lilacs.

At 32 weeks, it's nearly mid-May and you are round and curvy.

You're still walking. Slowly, like a camel. You discover Thoreau was right. You ruminate. A name for the new boy? Who will he be in this world? Who will I be? Will your favorite boy in the world love being an older brother?

You look around and see a flower bed full of dahlias, hundreds of petals, as if the flower couldn't stop itself. It's like looking into the face of a beloved. When a pack of cyclists streaks by right behind you, upsetting the air, you shout, "Hey! Come on! Slow down!"