Staying active before, during, and after pregnancy is important for your health and that of your baby. Here's how it should work....

6 months before conception: Schedule an appointment with your gynecologist to discuss your optimal weight and fitness goals for pregnancy.

3 months before conception: If you don't already have a regular fitness routine, Bob recommends aiming for up to five hours of cardio and one and a half hours of strength training per week.

First Trimester: Talk to your doctor about a safe maximum heart rate. Don't forget to drink plenty of water—it's easier to get dehydrated during pregnancy.

Second Trimester: You can continue working out as normal, but avoid exercises in which you have to lie flat on your back, which can restrict blood flow to the upper part of your body.

Third Trimester: Be extra-careful with balance exercises. In addition to the obvious shift in your center of gravity, your body secretes a hormone that relaxes your joints, further inhibiting stability.

Immediately postpartum: Rest up for four to six weeks before returning to the gym. Your hip and pelvic joints will be looser and need the break.

6 weeks postpartum: Ease into your regular (prepregnancy) workouts. Be patient about weight loss, and aim to keep your heart rate where it was during the first trimester.

2 months to 1 year postpartum: It's safe to increase your workout intensity—and once you do, you may find that the weight comes off faster than you expected. Moms who were fit before giving birth have an easier time getting back their pre-baby body.

More O makeovers: The full "Make Me a Ten!" series