TORONTO - Fifteen women, all in varying stages of pregnancy, splash to the beat of the music in the pool, while their instructor paces the deck and shouts for them to "twist it out," followed by directions to sprint and "push, push" -- words that foreshadow what they'll be doing in a few weeks as they give birth.

Over the next 45 minutes, the women will stretch, jump, float and use noodles and flutter boards as part of a fitness routine that's specially tailored to women in their second and third trimester of pregnancy.

Katherine Hyrcza is a glowing eight months pregnant, and says she joined the class for two reasons.

"It's the networking with other women and listening to their experiences, as well as the exercise part which gets my endorphins going," she said during the conversation portion of the class that preceded plunging into the pool.

"The buoyancy helps.You feel free and weightless.

It's just easier to do a lot of the movements that would've been much harder on land.''

Julie McLachlan, also eight months pregnant, agreed. "When you're in the pool you don't feel really like it's a huge workout ...but the next day, you definitely...feel it.

So it's comforting to know also that you're not putting a lot of pressure on your bones and your joints, and you're not overworking yourself."

Instructor Trish Del Sorbo, director of Baby & Me Fitness, noted that some pregnant women feel more comfortable exercising in the water. "There are some advantages to water fitness. Number 1 is that your core temperature just tends to stay cooler because you are in the water, so it's a constant cooling effect," she said.

"The water doesn't allow you to do quick jarring motions. So you can do the twists, the rotations, the floating.

Women can jump, they can run in the water, which is generally not recommended on land." She also suggested that it can be a safe way for a woman to exercise if she's carrying twins.

"I've had women pregnant with twins who've gone right till the end," she said.

Michelle Mottola, director of the R. Samuel McLaughlin Foundation exercise and pregnancy lab at the University of Western Ontario, said every expectant mother should have medical approval or screening by her doctor, midwife or nurse practitioner before entering into an exercise program.

Mottola is the co-author of PARmed-X (physical activity readiness medical examination) for pregnancy guidelines to help determine whether a woman should exercise.

The guidelines can be obtained through the Canadian Society for Exercise Physiology, she said. "Usually we suggest that they wait until after their first trimester, which would be the first three months. So any time after 12 weeks, if they're medically cleared, they can start an exercise program," Mottola said from London, Ont. Some women during their pregnancies may be susceptible to lower back pain and pelvic pain, she said.

"Just the whole buoyancy in the water helps to get some of the pressure off the lower back. So that is a real bonus."

"And I think women just feel very relaxed in the water just because...as they're gaining weight during pregnancy, it just eliminates all of that pressure on their joints."

Meghan Hulsman, who is six months pregnant, has had problems with pinched nerves in her back.

"When I'm just at work and stuff, or I'm sitting on the floor or doing anything, I can't actually turn from side to side, and sometimes I can't get up normally, so being in the water is a really good way to exercise."

Her back doesn't hurt in the water, she said. "And after the class, I'm just definitely more relaxed, and I definitely am more physically active at home -- I'll actually clean the house," she said as her classmates chuckled.

Noelle Ryan, seven months pregnant, experienced joint pain to the point where she wasn't working and couldn't sit for more than about 10 minutes at a time.

"And through that period, I still came to these classes, so that was the only thing that I was doing," she said, adding that a chiropractor helped her resolve the joint problem.

Mottola said the water temperature for pregnant women should be below 30 C, and she advised against instructors putting them in the deep end.

"They should probably be immersed up to their chest and that gives them the buoyancy of the water, but they can also touch bottom if they have to so they're not working too hard."

Exercisers should err on the side of caution and make sure they're not overdoing it, she said.

The talk test is one method of checking whether they're OK.

"If they can carry on a conversation while they're exercising, then you know that they're exercising in an appropriate intensity."

A Brazilian study published last month in the journal Reproductive Health investigated the effects of an aquarobics class on pregnant women.

Seventy-one women were enrolled in the study, and about half of them were assigned to take a 50-minute class three times per week.

The researchers didn't find any harmful effect on the cardiovascular health of the women who took water aerobics.

"We found no statistically significant differences in the duration of labour or the type of delivery between the two groups," researcher Rosa Pereira said in a statement.

However, only 27 per cent of women in the aquarobics group requested analgesia, compared to 65 per cent in the control group.

This represents a 58 per cent reduction in requests." "I hope it's true," Hulsman said when talk turned to the findings during the aquafit conversation in Toronto.

Del Sorbo said she's noticed a shift in recent years in the prenatal expectations of women with respect to interventions such as an epidural to alleviate pain.

"Five years ago, everyone was 'whatever, just give me the drugs,'" she said. "Now you hear more, 'I would like to go as natural as possible, and if I don't make it, then I don't make it.'"

Mottola, meanwhile, said that if a pregnant woman is attending a regular aquarobics class, she needs to make the instructor aware of her condition.

"And then the instructor should also be aware of the Canadian guidelines for exercise during pregnancy, and either talk to the pregnant woman before the class or have a special opportunity for directly talking to the pregnant woman in the class and saying just be careful, watch for this or watch for that."