You already know that you should work out - that it's good for your brain and your body, your self-esteem and your sex life, that it can calm your nerves and even reverse disease.
Countless studies have shown the remarkable reach of fitness. And now, researchers are learning that the benefits of exercise may apply to a developing fetus. Earlier this month, two studies presented at the annual meeting of the Society for Neuroscience suggested that those who exercise during pregnancy could be giving their unborn child a neurological advantage.
One study followed a group of 18 pregnant women, starting in their first trimester, assigning eight to a sedentary group and 10 to an active one, in which they were asked to exercise at least 20 minutes a day, three times a week. Eight to 12 days after the women gave birth, researchers fitted the newborns with electrodes that measure brain activity in response to various sounds - an established test for memory, says Dave Ellemberg, a neuroscientist at the University of Montreal and one of the study's authors. Indeed, the newborns of active moms showed "more mature, more effective brain patterns," he says.
"What we found out is that there's this amazing transfer from what the mother does onto her child," he says, adding that moms-to-be can give their kids "a kickstart even before they're born." The team plans to follow up with the children when they're 4 to 6 months old to see how development progresses.
Another study, which used rats, found that the male offspring of rats that exercised during pregnancy had better object recognition as adults. This showed the potential of exercise to leave "long-lasting effects on the behavior and the cognitive function of the offspring," says David Bucci, an author of the study and professor of psychological and brain science at Dartmouth University. (Bucci was so surprised by the results that he had them triple-checked by the graduate student running the study.)
[Read: Best Foods to Eat During Pregnancy.]
There is still more research to do, but these studies may help to refute the popular and mistaken belief that when it comes to exercise, pregnant women should exercise extreme caution.
"There's been a legacy forever of pregnant people being somehow equated with eggs, that their shell is very fragile" and thus, "the baby is easily broken," says Roger Harms, associate professor of obstetrics and gynecology at Mayo Medical School and editor of the "Mayo Clinic Guide to a Healthy Pregnancy."
To the contrary, there's no evidence that exercise would harm a fetus and the health benefits for the mom-to-be are well-established, he says. As Harms sees it, exercise provides a kind of insurance for mothers to better rebound from the added weight and stress of new motherhood.
[Read: The Secret to Sticking With Exercise.]
"If you've already taken a hiatus from your exercise during pregnancy, you are probably going to have a hard time getting started again for the rest of your life," he says. But if people manage to exercise through the challenges of pregnancy, "the odds are pretty good you'll be able to overcome many of the impediments that are more social than physical after the baby is born that keep people from exercising." What's more, he says exercise helps provide "better energy for labor and delivery and all of the trials that come at the end of pregnancy."
So how much should pregnant women exercise?]
Thirty minutes a day to help modify weight gain, improve mood and comfort and prepare for labor, says Laura Riley, director of labor and delivery and obstetrics and gynecology infectious disease at Massachusetts General Hospital and author of "You & Your Baby: Pregnancy." "I think that people who exercise are less whiny, frankly," she says. "Whether they have fewer aches and pains I'm not sure, but they complain less because they're more mobile all through pregnancy, even at the end."
Which exercise is recommended depends on the person's fitness level. But in general, women should continue the exercise they already do - it will just become harder as they carry extra weight. And for those who don't do any exercise? Walk. "Put on a pedometer, that'll get you going," Riley says.
As for moves to steer clear of, avoid exercising from a flat-on-the-back position, which can cause back strain and impede blood flow that could lead to fainting, Harms says. Also, there's no point in doing abdominal work, since these muscles are being stretched to accommodate the baby, he says. Plus, you may want to reconsider workouts that hinge on balance, since a redistribution of weight can increase the odds of injury. "You do get clumsy," he says. "If you have always been a biker, consider a stationery bike."
You'll also want to avoid contact sports for obvious reasons. "Any sport where you have a high likelihood of falling and hitting your abdomen, that's going to be bad," Riley says. "Other than that, you can do almost anything, and people who are sort of in tune with their bodies will modify their exercise as the pregnancy progresses."
[Read: Prenatal Yoga: What You Should Know.]