For generations, pregnant women were advised to avoid any kind of exercise because of concerns that it might put the unborn baby’s health at risk.

They were also told to “eat for two” to make sure the baby received enough calories and nutrients to develop properly.

Well, both those pieces of advice are now terribly out of date, at least for most women, as an international trio of experts explain in a Viewpoint article published last week in the Journal of the American Medical Association (JAMA).

“Pregnancy is no longer considered a state of confinement; an active lifestyle during pregnancy is safe and beneficial. Most medical and scientific organizations promote physical activity in all phases of life, including pregnancy,” write Maria Perales of Camilo José Cela University in Madrid, Dr. Raul Artal of Saint Louis University in Missouri and Dr. Alejandro Lucia of the European University of Madrid.

Indeed, it is now widely acknowledged that the “misguided recommendations” of the past have been “a major contributor to the worldwide obesity epidemic,” leading to potentially lifelong health problems for mothers and babies alike, the three experts point out.

Too much weight gain

In the United States, 45 percent of women begin pregnancy overweight or obese, up from 24 percent in 1983, according to data from the Centers for Disease Control and Prevention. And 43 percent of pregnant women gain more weight than is recommended.

Those recommendations, which come from the National Academy of Medicine (formerly the Institute of Medicine), are no more than 25 to 35 pounds for normal-weight women, 15 to 25 pounds for overweight women and 11 to 20 pounds for obese women. (The weight categories are based on body mass index, or BMI.)

Excessive weight gain during pregnancy can lead to serious health problems for both mother and baby. Women who are overweight or obese are at greater risk of pregnancy-related complications, including preeclampsia (a condition marked by high blood pressure) and gestational diabetes. Their babies are more likely to be born prematurely, which can lead to health problems.

Some research also suggests that children born to mothers who are obese are at greater risk of developing diabetes, heart disease and obesity later in life. 

A major benefit of exercise during pregnancy, the experts point out, is the prevention of excess weight gain. And some studies have shown that exercise during pregnancy is also associated with a decreased risk of pregnancy-related complications, including gestational diabetes, preeclampsia, Caesarean birth and having a baby that is significantly larger than average. 

Safety concerns

In the past, doctors were concerned that exercise during pregnancy might increase the risk of a baby being born too early. But research has debunked that idea. A 2015 meta-analysis showed, for example, that for women with uncomplicated pregnancies, aerobic and muscle-toning exercise of moderate intensity three to four times a week for 35 to 90 minutes per session did not increase the risk of preterm birth. 

Other research has shown that it’s safe for most sedentary women to begin exercising during pregnancy.

“Contrary to previous opinions, pregnancy is now considered an ideal time not only for continuing but also for initiating an active lifestyle,” write the Viewpoint experts.

It’s even considered safe, they point out, for women with certain risk factors, including gestational diabetes and chronic (not pregnancy-induced) high blood pressure.

Of course, every woman should talk with her doctor before continuing or starting any exercise program during pregnancy. And pregnant women should take several precautions when they do exercise. Stay hydrated. Avoid excessive heat and humidity. And halt the activity at the first signs of a potential health problem, such as vaginal bleeding, dizziness, chest pain, headache and leg pain or swelling

How much and how often?

The Viewpoint authors urge all pregnant women without any medical complications or contraindications to follow the latest guidelines from the American College of Obstetricians and Gynecologists, which are essentially the same guidelines as those for adults who aren’t pregnant: “Engage in aerobic and strength exercise at moderate intensity at least 10 to 30 minutes per day on most days of the week.”

Low-impact activities — such as walking, aerobic dancing, stationary cycling or swimming — are recommended. Moderation is key.  Pregnant women should avoid exercise that causes their heart to pump at 90 percent or more of its maximum beats per minute, the Viewpoint authors stress. And strenuous aerobic exercise — such as long-distance running and frequent heavy weight lifting — should be avoided, they add.

The article also points out that the benefits of yoga and Pilates during pregnancy have not been demonstrated, although “yoga is thought to be effective for improving mental and health and reducing pain.”

FMI:  You can read part of the Viewpoint article on the JAMA website, but the full article is, unfortunately, behind a paywall.