1. Consult with your obstetrician.
It is best to do this prior to conception so that you are already following safe guidelines when you become pregnant. Certain medical conditions and pregnancy-related complications may be exacerbated by exercise, so a detailed discussion with your obstetrician is important.
2. Avoid injury.
During pregnancy, ligaments become more flexible, looser, and thus more prone to injury. It is therefore important to carefully warm up before and cool down after exercise, as well as to avoid rapid, ballistic movements, deep flexion or extension of joints, and uneven exercise surfaces. This propensity to injury also applies to weight lifting so changing to lower weights may be necessary.
3. Maximum heart rate should be lower than 140 beats per minute.
Above this level, blood may be diverted away from the pregnant uterus to the exercising muscles, thus putting the fetus at risk. This guideline often results in women changing from jogging to walking, from high impact to low impact aerobics. Of interest, there is a natural tendency for pregnant exercisers to decrease their intensity.
4. Drink plenty of water.
This is very important because during pregnancy you are more prone to dehydration. Drink before, during and after you exercise. This will also help to keep your temperature from rising too high. (See below)
5. Keep your body temperature below 100.4 degrees F.
Obviously, it is not possible to work out with a thermometer under your tongue at all times. However, if you occasionally check your temperature during your work out at periods of peak exertion, you can find your core temperature. Temperatures above 100.4 degrees F (whether due to exercise, afebrile illness, saunas, etc.) in the first trimester have been associated with certain birth defects.
6. Eat appropriately.
Caloric intake should be adequate to meet the needs of pregnancy and exercise. (This should not be interpreted to mean that because you exercise, you can eat anything and everything you desire).
7. Avoid the supine position.
After the fourth month of gestation, avoid lying on your back for exercises such as sit-ups, leg-lifts, or even stretching exercises. At this point in pregnancy, the uterus is large enough to obstruct blood flow to you and your baby when you are in this position.
8. Certain sports are to be avoided during pregnancy.
These include horseback riding, downhill skiing, water skiing, scuba diving, surfing, body surfing, contact sports, and any activity that may result in a fall. (For many of us that may including biking, skating, etc).
9. Listen to your body.
The changes your body undergoes during pregnancy are many and profound, but they all occur to create a healthy fetus, so listen to yourself. If you experience pain, uterine contractions, vaginal bleeding, dizziness, palpitations, or other concerning symptoms, stop exercising and alert your physician.
Exercise during pregnancy is a nice means of maintaining some control of your body. It helps you to avoid excessive weight gain and has been shown to help women with their labors and deliveries, but most of all it should be fun for you.