Is exercise safe for pregnant women

Exercise is beneficial for those who exercised prior to pregnancy and for those who start after becoming pregnant. Exercise will improve circulation and help decrease pregnancy related edema that often occurs in the extremities. It will also improve mood and help alleviate some discomforts associated with pregnancy.
Exercise training can reduce the risk of developing preeclampsia and gestational diabetes. Chronic exercisers are more likely to deliver normal size babies and less likely to have delivery complications. Research suggest that exercise training is safe and does not increase maternal or fetal risk. Any women who has a low risk pregnancy and is cleared by their doctor, can start an exercise program.
The American Congress of Obstetricians and Gynecologists recommends that pregnant women accumulate 30 minutes of moderate intensity exercise on all or most days of the week. Activities should include aerobic and resistance training and include a long warm-up, cool down, and stretching. Women who develop any contradictions while training, should immediately stop and consult their doctor before exercising again.
Below are the recommendations from ACSM for women who are pregnant.
Aerobic
Frequency - 3-5 days a week
Intensity - Moderate intensity
Time - 30 min or more. Accumulating 150 min/week
Type - A variety of weight and non-weight bearing activities
Resistance
Frequency - 2-3 nonconsecutive days a week
Intensity - 12 to 15 reps to be performed to a point of moderate fatigue
Time - 2-3 sets targeting major muscle groups
Type - A variety of machines, free weights, and body weight exercises
Flexibility
Frequency - 2-3 days a week. Daily would be most effective
Intensity - Stretch to the point of feeling tightness or slight discomfort
Time - Hold static stretch for 10-30 seconds
Type - A series of static and dynamic flexibility exercises for each muscle tendon unit