HAVING given herself just three months to get her body back into its 120-lb., cat walk-ready shape, proud new mother Cindy Crawford can’t af ford to sit around eating candy bars.

Instead, the leggy 5’9″ stun ner, who gave birth to baby son Presley on July 2, has engaged the services of her New York trainer and close friend, exercise guru Radu – who says he kept a close eye on her fitness during the pregnancy itself, which is key to regaining form post-deliv ery.

Already, he says, Cindy has resumed daily walks on her treadmill, as well as some light exercise and stretching.

By the end of August, Radu fully expects the supermodel to resume her normal workouts. During the first two months of Cindy’s pregnancy, Radu took a cautious approach to her normal workout – an hour and a half, four times a week. “I didn’t want to take any risk of causing harm to the baby,” he says. (Most miscarriages occur within the first eight weeks of preg nancy.)

Radu kept Cindy’s metabolic rate up by having her exercise for longer periods of time at a lower intensity – instead of running for 30 minutes, for ex ample, he had her walk for 45.

But once Cindy hit her second trimester, Radu had her resume her traditional workout for the next three months.

After a five-minute warm-up, Cindy did 30 minutes of aerobic activity to burn calories – usually treadmill running or stair climbing. Then came calis thenics, such as jumping and squats, to build strength and in crease endurance. Finally, upper- and lower-body strength training and abdominal exer cises tightened and toned Cin dy’s body.

As she neared her last trimes ter, Cindy replaced one to two of her four weekly workouts with maternity yoga classes – excel lent during pregnancy since yoga strengthens muscles with out adding undue stress to the body.

As Cindy became increasingly uncomfortable with her extra weight, Radu had her switch from running to walking. He also modified her abdominal workout. (Crunches aren’t rec ommended after the third month of pregnancy because they put pressure on the abdo minal wall, upping chances of hernias, says Dr. Gideon Pan ter, a Manhattan obstetrician- gynecologist.) Instead, Cindy did exercises such as side twists and elbow-to-knee lifts, which involve less abdominal strain.

It’s generally safe to continue your normal exercise program during pregnancy, says Dr. Pan ter, provided you don’t overdo it – you should be able to hold a conversation while you work out. He particularly recom mends swimming and brisk walking as good aerobic exercise that won’t overtax your body.

Panter also says it’s fine to re turn to light walking a week after pregnancy, but hold off on your normal workout (including abdominal exercises) until six weeks after giving birth.

That’s exactly what Cindy is doing.

On her return to New York in late August, Radu says he’ll spend the first two weeks easing Cindy into her workout with light cardio, weights and flexi bility exercises. The third week, he’ll add back her regular swings, lunges, running drills, broad jumps and squats.

“By September,” he pro nounces, “she’ll be back to her pre-pregnancy form.”

Diet is equally important for keeping pregnancy weight off, says Manhattan nutritionist Joy Bauer.

Pregnant women require about 150 extra calories a day during the first trimester, and around 300 extra calories a day during the last six months. (Breast-feeding moms also re quire an additional 300 calories daily.)

The best way to get these extra calories is by upping your intake of fresh fruits, vegetables, whole grains, low- fat dairy (like skim milk) and lean sources of protein such as chicken and fish.

The first three months of her pregnancy, Cindy battled morn ing sickness by sticking to car bohydrate-rich foods, such as ce real and baked potatoes. These foods are easy to digest and pro vide your body with energy – plus, fortified cereal is a good source of valuable nutrients such as iron and folic acid, says Bauer.

In Cindy’s second trimester, her queasiness had subsided, and she resumed her usual low- fat diet of chicken, pasta and salad (although she occasionally gave in to her cravings for red meat and Taco Bell burritos).

She did, however, have to give up her sushi – raw fish may harbor bacteria potentially harmful to the fetus.

Cindy was also smart to drink tons of water throughout her pregnancy – at least 10 8-oz. glasses daily. This extra fluid helped deliver oxygen and nutri ents to the fetus and also helped alleviate common pregnancy problems such as constipation, says Bauer.

On average, women gain about 30 lbs. during pregnancy, 20 of which are usually lost within about a month of having the baby, according to the American Council on Exercise.

To lose those last five to 10 lbs., new moms should adopt a workout regimen that combines both aerobic activity (to burn calories) and strength training (to tone and tighten problem areas, especially the stomach, thighs and buttocks), says Dr. Char lotte Sanborn, director of women’s health research at Texas Women’s University.

While you should always con sult with your doctor before starting any exercise program, the American Council on Exer cise recommends four days of aerobic exercise for 30 to 45 minutes a week.

To tighten and tone muscles, try some of Cindy’s exercises, which she’ll resume with Radu in late August (below). For all of these, unless otherwise indi cated, you’ll want to start with three sets of 10, gradually work ing your way up to 25 reps. (Im portant note: Consult with your doctor before trying any of these exercises.)

Picture #1: lateral leg swings

Works: thighs and buttocks

Stand arm’s length from a wall, and place both hands on the wall for support. Cross your right foot in front of your body, then swing it straight out to the side. Swing the leg from side to side in a continuous motion. Switch legs, and repeat.

Picture #2: adductors

Works: outer thigh and but tocks

Lie on your right side, left hand on the floor in front of you for support. Bend your left leg, and place your left foot flat on the floor behind your right thigh. Raise your right leg straight up toward the ceiling, foot pointing forward. Lower and repeat, then switch sides.

Picture #3: front lunges

Works: legs

While standing, lift your left leg, keeping your knee bent 90 degrees and your thigh parallel to the floor. Step far forward with your left leg, extending your right leg and lowering your body toward the floor. Let your right leg straighten. Push back and up from your left toe to your heel, bringing your knee up to starting position. Repeat six times.

Picture #4: modified bench press

Works: shoulders, chest, arms

Lie on your back, knees bent, holding a dumbbell in each hand (start with 3-lb. weights). Extend both arms toward the ceiling, palms facing forward. Bring elbows toward the floor, then straighten arms back to ward ceiling.

Picture #5: lateral flies

Works: chest, arms

Lie on your back, knees bent, holding a 3- to 5-lb. dumbbell in each hand, arms extended to ward the ceiling, palms facing in and elbows slightly bent. In haling, open both arms wide to the sides as far as you can. Ex hale, and return to starting po sition.

Picture #6: broomstick twists

Works: abdominals

Stand, feet slightly wider than shoulder-width apart, knees re laxed. Hold a broomstick behind your neck and twist from side to side, keeping your hips facing forward. Do six to 10 reps.

Picture #7: Elbow-to-knee lifts

Works: abdominals

Standing, place your hands be hind your neck and bring your right elbow down toward your left knee while bringing the knee up toward the elbow. Re turn to start, and repeat with left elbow and right knee. Con tinue alternating sides without stopping until you have done six to 10 reps on each side.

For more information about Radu’s workouts, check out his book, “Radu’s Simply Fit” (Cader Books, 1996).

Pregnancy Do’s and Don’ts

For a healthy pregnancy, fol low these exercise tips, courtesy of Dr. Hilda Hutcherson, as sistant professor of obstetrics and gynecology at Columbia University Medical School:

Do’s

Aerobic activity (running, walking, swimming) for at least 30 minutes, three to four times per week

Kegal exercises to strengthen your pelvic area (your doctor can tell you how to do them)

Double your normal water in take while exercising (one 8-oz. glass of water every 15 minutes)

Yoga or light stretching exer cises once or twice a week

A five- to 10-minute series of warm-up exercises and stretches before beginning your workouts

Don’ts

Exercising flat on your back after the 12th week of preg nancy

Crunches after your 12th week of pregnancy

Activities that require rapid changes in direction – like high-impact aerobics or running drills

Working out so hard you can’t carry on a conversation

Exercising through nausea, dizziness, amniotic fluid leakage or vaginal bleeding