When you’re pregnant and feeling tired and achy, exercise might be the furthest thing from your mind. But from lowering the odds of complications during birth to boosting a newborn's brainpower, studies show there are many benefits of exercise during and after pregnancy.

Yet, despite the growing research, many women are still unsure about what’s considered safe, and what might be pushing too far.

Dr. Manny Alvarez, an Obstetrician-Gynecologist and the senior managing health editor of FoxNews.com, recently sat down with physical therapist and author of "Your Best Pregnancy," Dr. Denise Jagroo to debunk some of the most common pregnancy exercise myths.

Jagroo runs a private physical therapy practice in New York City that specializes in pelvic, obstetric and orthopedic dysfunctions. She has taught hundreds of women how to stay healthy during their pregnancy through safe and proper exercise techniques.

“Women are still intimidated by the idea of exercising too intensely from old theories and old guidelines, but exercise during pregnancy is safe-- as long as the woman is not high risk and if they’re cleared by their obstetrician,” Jagroo told FoxNews.com.

According to the American College of Obstetrics and Gynecology (ACOG), exercising for at least 30 minutes on most days of the week can help mothers-to-be feel better both mentally and physically in the following ways:

-May prevent or treat gestational diabetes
-Promotes muscle tone, strength, and endurance
-Helps reduce backaches, constipation, bloating, and swelling
-Improves your mood
-Increases your energy
-Helps you sleep better

When it comes to knowing how much exercise is safe during pregnancy, Jagroo suggests following the “talk test.”

“I always tell them [pregnant clients] to exercise with a buddy and if they can say a full sentence without gasping for air or overheating they’re OK,” Jagroo said, adding that the old guidelines of having a target heart rate of 140 beats per minute was thrown out in 1994 by the ACOG.

And for women who regularly exercised before pregnancy, they can continue doing the exercise routines that they’ve done in the past, Jagroo said.

“If they were exercising before, I would say they can continue doing what they were doing-- their bodies are used to it,” she said. “It all depends on what their activity level was before. The safe thing is walking and light weights. If someone was a runner you can still run throughout the pregnancy, but there are things you need to modify; shoe size for swelling, time of day you’re running, what surfaces you’re running on, making sure you’re tying your shoes properly.”

Other safe exercises include swimming, cycling and light aerobics to keep the heart and lungs strong.

Although several fitness options are available, there are several factors to be careful about and special modifications to consider, like walking on hilly terrain.

“They also have to be careful about where they’re walking, especially long or steep hills because we don’t want too much rotation on the pelvis to cause any distress on the side joint in the back or the public symphysis in the front, so I tell them to walk on flat ground, [and to] take shorter steps,” Jagroo said.

Working out in a gym is a safe environment for most women, but Jagroo warns women to be cautious when asking personal trainers at sports clubs for advice.

“Make sure the person, the personal trainer, yoga instructor or the women’s health specialist has proper prenatal training because I’ve seen many videos online and I’ve seen many personal trainers -- and not to knock personal trainers or prenatal yoga instructors -- but I’ve seen them put people in positions that are dangerous,” she said.

Some floor positions that have women on their hands and knees for long periods of time can be too strenuous on the abdominal connective tissue and muscles and can cause abdominal separation, also known as diastasis recti.

Diastasis recti is a common condition among pregnant women and in some cases can cause a woman’s stomach to stick out more than normal. Some call it a “pooch.”

With so much information about which exercises to do and not to do, here are 4 myths Jagroo says to be aware of:

1. Too much exercise will take nutrients away from the baby

MYTH

“Nutrients are always going to be shunted to the baby first, and filtering gases are always going to be enough because there’s an increase in blood volume during the pregnancy, and the placenta cushions the baby enough,” Jagroo said.

2. Running is too jarring for the baby

MYTH

“There have been marathon runners who have run throughout their pregnancy. But as long as the mother is making sure that she’s on safe terrain and with safe footwear; that her shoes are tied properly (even though she can’t see her feet), she and her baby should be fine. It’s usually a comfort level for the mom on whether she wants to keep running into her 3rd trimester,” she said.

3. Avoid prenatal yoga, it won't help you stay fit

MYTH

“Again you have to be careful with the positions in yoga classes– I wouldn’t recommend certain positions that call for the woman to be on her hands and knees or extension exercises (leaning and curving your spine backwards). During pregnancy, the woman’s center of gravity is already so far forward and there’s already so much stress on the ligaments and disks in the spine, I wouldn’t want them to extend so much--- but I do love that yoga focuses on breathing and stress reduction.”

4. Ab crunches are safe to do

MYTH

“There are specific ones you should avoid. Women should not be doing crunches or anything where they’re going from laying down to sitting up. Even getting out of bed, they shouldn’t be going straight up because the abdominal muscles can split.”

Some safe ways to keep your abs strong can include sitting on an exercise ball and lifting one leg off the floor, one at a time. You can also try lifting one arm up while lifting the opposite leg, but these need to be in controlled movements.

Women can usually return to their normal abdominal work and more aggressive exercise routines about two months after having a baby, Jagroo said.

“And before the 6-week postpartum checkup, they can do simple things like Kegel exercises, stretching, walking and breathing exercises-- but nothing aggressive, you still have pregnancy hormones coursing through the body and still affecting the libia albia structure in the abdomen,” she said.

For more information visit DrJagroo.com.