Thirty minutes of daily exercise is recommended for a healthy pregnancy, and cold weather is no reason to make an exception. Regular exercise is good for muscle flexibility, healthy circulation and warding off depression. However, many popular winter sports entail risks that make them poor choices during pregnancy.

In considering the safety of the variety of winter activities, keep in mind the general recommendations for healthy exercise during pregnancy:

• Avoid sports where you may fall or incur direct trauma to your belly. Activities that result in high impact to the uterus could lead to placental abruption, a dangerous condition in which the placenta pulls away from the uterus.
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• Physical activities that involve sudden stops or starts or rapid changes in direction could make you prone to joint injuries. Your ligaments begin to soften during the second half of pregnancy. While this flexibility may be helpful during the actual birthing process, it puts you at higher risk for joint injuries.
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• Be careful with activities that rely on careful balance. Your center of gravity changes as your belly grows during pregnancy, altering your sense of balance.
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• High altitudes may make it more challenging to meet your oxygen needs, increasing your breathing frequency and heart rate. You may feel lightheaded or queasy until your body acclimates to the higher altitude. It is unadvisable to participate in sports at altitudes higher than 6,000 to 8,000 feet without having sufficient time to acclimate.
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• Take breaks from exercising if you notice that you feel short of breath, physical pain, fatigued or overheated. And even before you feel thirsty, it's important to keep well hydrated. Drink extra fluids before, during and after exercising.
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• Only exercise if your health care provider has assured you that it is safe to do so. Some reasons to curtail exercise during pregnancy include a history of preterm labor, vaginal bleeding, severe anemia, fetal growth retardation, poorly controlled hypertension and having a heart arrhythmia.
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  When we apply these general recommendations to specific winter activities, we see that many popular winter sports should be discouraged during pregnancy.
  
  Downhill Skiing. The two main concerns are exercising at a high altitude and the possibility of injury. It's clear that only experienced skiers should be on the slopes during pregnancy. However, even if you can ski without falling you cannot control the actions of others on the mountain. If you fall by your own doing or due to reckless behavior of other people, you could threaten the safety of your pregnancy.
  
  Snowboarding. This sport makes you vulnerable to falling or collisions, and therefore is not recommended.
  
  Cross-country Skiing. If you are experienced and unlikely to fall, this is a safer way to exercise in the snow. Choose trails at lower altitudes. Bring fluids to drink and dress in layers, being sure to adjust your outfit if you begin to overheat.
  
  Sledding. If your family and friends want to go, you're better off taking the pictures. The potential for falling is too high to recommend this activity.
  
  Snowshoeing. This is a safer way to explore mountain snow, however your level of exertion will depend on the terrain. Snowshoeing is fine if you keep well hydrated and can maintain a heart rate below 150 beats per minute.
  
  Ice Skating. As your pregnancy advances, your center of gravity shifts forward, making balance more challenging. Ice skating may be continued during pregnancy if you are an experience skater, can maintain your balance and are unlikely to fall. On the other hand, this is not the time to learn how to skate.
  
  Although many winter sports may not be appropriate during pregnancy, there are lots of way to continue staying active during the winter. Many pregnant women continue exercising in the warmth and safety of an indoor facility. Low impact aerobics, weight training, using an elliptical trainer and swimming are all good bets. Walking is fine if the path is not icy. And, if you're housebound, don't forget the option of listening to your favorite music at home and dancing!