Prenatal yoga is a great low-impact workout that stretches and strengthens.

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Doctors recommend getting regular exercise throughout pregnancy, but the idea of pounding away on a treadmill may not be too appealing to many women with rapidly expanding bellies. That's one reason prenatal yoga is so popular among expectant moms; it's a low-impact, low-intensity workout that seems to have some real benefits -- both physical and psychological.

Most prenatal yoga classes include stretching and breathing exercises, both of which can help improve sleep, reduce stress, and decrease some of the aches and complications associated with pregnancy, such as lower back pain, nausea, headaches, and shortness of breath. Studies have even shown that yoga can help decrease your risk of preterm labor or pregnancy-induced hypertension, and your unborn baby's risk for a condition called intrauterine growth restriction. [Source: Mayo Clinic]

Yoga during pregnancy seems to have some serious mental health benefits, as well: A 2012 University of Michigan study found that expectant moms who practiced yoga were less likely to experience depressive symptoms and also reported feeling a stronger bond with their babies. [Source: Muzik]

It's safe to try prenatal yoga even if you've never done regular yoga before, says Jen Oppenheimer, a prenatal instructor at New York Sports Club in Manhattan, but don't jump into anything more strenuous than the exercise you're already used to.

Avoid Bikram yoga and "hot yoga," and make sure you can stay cool and hydrated during class. (If you're a newbie to yoga, you may also want to stay away from vigorous Vinyasa, Ashtanga, or "Power Yoga" styles, and opt for more restorative classes, instead.) [Source: Mayo Clinic]

If you're not taking a class that's designated specifically as prenatal, it's important to make sure your instructor knows that you're pregnant -- and how far along you are -- so that he or she can help you modify postures that may be too difficult or risky.