It's tough to know how many people suffer postpartum depression. For women, it's thought to be 13% or more (there's some indication that men suffer from it as well).

And it has increased dramatically over the past decade or so, with a 60% growth among whites and a 140% increase among Blacks, according to a study in the American Journal of Obstetrics and Gynecology (ACOG).

The increase in postpartum depression can be correlated with the increases in sedentary behavior and obesity.

The good news: A study in BMJ Sports Medicine has found that as little as 80 minutes weekly of moderate-intensity exercise — such as brisk walking, water aerobics, stationary cycling, or resistance training — cuts the risk for postpartum depression nearly in half, and eases the severity of depression and anxiety if it does occur.

According to ACOG, you should consult your obstetrician before starting an exercise routine when you're pregnant. Ask about modified yoga and Pilates routines. Experienced runners or joggers should discuss how to continue the activity during pregnancy.

If you are overweight or obese, we also suggest you talk to a nutritionist to learn how to manage potential pregnancy weight gain that will make exercise — and pregnancy — more difficult. (If you’re not yet pregnant but are thinking about it, make a plan to lose weight first.)

For more help having a happy postnatal experience, check out our books "YOU: Having a Baby" and "YOU: Raising Your Child."