Today, On Parenting launches a new feature called “Expert Advice.” Every week, I’ll ask an expert for advice on a parenting issue that’s in the news or that readers have asked me to research. I’ll post the answers each Thursday (unless news warrants a faster response).

Amber Miller holding her baby, June, after running the Chicago marathon. (Amy Jo Steinbruecker/Reuters)

She also made many of us wonder: How much exercise is healthy during pregnancy?

I posed the question to Jennifer Middleton, the owner of the D.C. franchise of Stroller Strides, a national fitness group geared to pregnant women and parents of stroller-bound kids. (Full disclosure: I used to be active in the group and, for a spell, an instructor.)

Middleton is a certified trainer with a speciality in working with pregnant women, so it’s no surprise that she’s a big proponent of exercise during pregnancy. Still, Middleton said there are five things pregnant women should keep in mind.

1.  Consult with a doctor: Be sure to get a physician’s approval to exercise during pregnancy. Exercise is good for both mom and baby, as long as there are no contraindications during your pregnancy. In fact, almost all pains and discomforts that go along with pregnancy can be decreased or eliminated with exercise.

2.  Find a pre-natal fitness professional or class: Pregnancy has profound effects on almost every physiological system in a woman’s body. There are certain symptoms pregnant women can experience during exercise that are reasons to stop immediately and seek medical help. Vaginal bleeding, unusual shortness of breath, dizziness, headache, chest pain, unusual muscle weakness, and calf pain or swelling are a few. Especially when venturing into exercise for the first time, be sure it’s under the supervision of an instructor who has been trained in the unique aspects of pre-natal fitness and who is aware of the signs of when exercise should cease.

3.  Listen to your body: If it hurts, don’t do it. Now is not the time to push through the pain. Monitoring heart rate is no longer the proper way to measure exercise intensity during pregnancy. Instead, it’s best to use the Rate of Perceived Exertion. The focus is not to exercise to the point of exhaustion. New aches and pains may appear during pregnancy in ankles, knees, hips, upper and lower back, and wrists, so be cautious and safe.

4.  Modify movements: The hormone relaxin is present in expecting moms to help the body with pregnancy and delivery, and loosen the joints. Be careful of lateral or side-to-side movements and balance exercises. Sports or activities that could risk abdominal injury should be avoided.

5.  Aim for three days per week: The American College of Sports Medicine says regular exercise is preferred over intermittent activity for pregnant women. Three times per week is recommended.