Physically fit pregnant women have less back pain, easier delivery and better metabolic health. Most fit women can continue training during pregnancy (with some modifications), but untrained women should begin conservatively and do only mild- to moderate-intensity exercise.

Pregnant women should avoid exercises that might traumatize the fetus (unborn baby), trigger high body temperatures or compromise blood flow to the fetus.

During weight training, avoid exercises that challenge balance and require good hip mechanics, such as lunges, squats and barbell lifts off the floor (e.g., deadlifts and cleans).

Machine exercises that support the body are best because they present less risk of injury. Do short duration, static exercises (10 seconds), such as side-bridges and bird-dogs (static back exercise) to stabilize core muscles and prevent back pain.

Breathe normally when lifting weights and don’t strain during the exercises. Resistance training is a safe, valuable type of exercise for pregnant women as long as you take precautions. [sources: Strength and Conditioning Journal, Fitness RX]