When it comes to pregnancy, Heidi Klum is the anti-Christ. Not only has she delivered three children in as many years, but her body has rebounded-to Victoria’s Secret’s expectations no less-each and every time. Her secret? A comprehensive fitness routine during pregnancy (and freaky German supermodel genes.)

But even if you don’t plan on strutting down the fashion runway on the way home from the maternity ward, working out while you’re waiting for your little bundle of joy to debut has many benefits. Physically, exercising while pregnant can reduce aches and pains, prevent wear and tear on your joints (which become loosened during pregnancy) and help your body snap back more quickly after delivery (although I can’t promise you’ll ever look like Heidi!). In addition, a good fitness plan can help temper mood swings (not that the hormone-fueled emotional rollercoaster pregnancy invokes isn’t a laugh-a-minute), reduce fatigue and improve sleep. Still need convincing? Women who exercise have shorter and less intense labors.

But before you tie yourself to the treadmill for the next nine months, there are a couple of things to consider. First and foremost, a healthcare practitioner is the only person who can tell you whether it is safe for you to exercise. Some reasons they may request that you lie low during pregnancy include spotting and bleeding throughout the pregnancy, risk factors for pre-term labor or premature rupture of membranes. However, for most of us, exercise is perfectly safe-and wholeheartedly encouraged-by the medical community when the following guidelines are followed:

To Do:
* Select a fitness program that includes cardio, strength training, and flexibility components.
* The American Pregnancy Association generally recommends that cardio training be limited to between 15 and 30 minutes and should include low-impact cardiovascular activities such as brisk walking, running, elliptical, biking, or low-impact aerobics classes. Athletes and other highly fit individuals, meanwhile, are authorized to work out for longer periods, but again, should consult their physician regarding their proposed fitness routine.
* Pregnant women should keep their heart rate during cardiovascular activities to no more than 140 beats per minute.
* When strength training, pregnant women should be sure to train the shoulders, upper back, chest, and arms (trust me, when you’re schlepping around a 10 lb baby, you’ll appreciate the advanced training.)
* Abdominal exercises are also encouraged throughout pregnancy, although personal trainers recommend that you sub conventional sit-ups and crunches (which are both strictly prohibited after the first trimester because they can reduce blood flow to the fetus) for pelvic tilts in either a standing, seated or all fours position.
* Pregnant women are also encouraged to stretch before and after workouts. Specifically, women are advised to stretch their hamstrings and backs (which become strained as a women’s burgeoning belly-and boobs-throw off her center of gravity). Ankle rotations are also recommended to reduce swelling, although personal trainers recommend against foot flexion during pregnancy as it can result in calf cramps.
* Although recommended as part of any fitness program, warm-ups and cool-downs are particularly important during pregnancy to allow the mother’s heart rate and blood pressure to adjust in a slow, safe and controlled manner.
* Shell out for new sneakers. During pregnancy, feet can increase as much as two full sizes and, perhaps even worse, the effects can be permanent! When shopping for new kicks, select a pair that provides good ankle stability and has added arch support.
* It is especially important for women to remain hydrated during exercise. Experts recommend that women drink one pint of water prior to exercise and an additional cup for every 20 minutes of sustained activity to maintain optimal hydration.
* Eat up! While you aren’t technically “eating for two,” pregnant women – and particularly those who exercise – need to be sure to scoff an additional 150 to 300 calories per day (pickles and ice cream anyone?)
* Listen to your body. Exercising while pregnant results in a higher-than-normal increase in oxygen demand (likely due to the baby pushing up against the diaphragm and reducing its ability to expand and contract), meaning that you will feel tired more quickly.

To avoid:
* Avoid contact sports (football, softball, even ultimate Frisbee if you’re so inclined) as well as those activities that include bouncing, springing, leaping, or movements that are jarring or involve a sudden change of direction. Experts also recommend that you lay off horseback riding and scuba diving (which is probably why you have yet to find a maternity wetsuit!)
* Now might be the time to pair up with a senior citizen and launch your mall walking career because you, little lady, need to avoid exercising on rough or uneven terrain. The reason? Looser joints and ligaments paired with an unnatural center of gravity means the risk of falls (and serious injury) are far higher.
* Providing further evidence that mall walking might be the way to go, experts recommend that pregnant women avoid exercising in temperatures exceeding 102.6 degrees Fahrenheit. This guideline is particularly important during the first trimester, when fluctuations in body temperature
can lead to congenital abnormalities, but should also be followed during the second and third trimester (when even walking to the fridge causes you to break a sweat!)
* Pregnant women should also avoid exercise movements that require standing or holding one position for a prolonged period of time as well as any movements that strain the lower back (such as lifting a weight above the head or deep squats.)